U.S. patent number 9,270,443 [Application Number 14/609,924] was granted by the patent office on 2016-02-23 for serial data transmission circuit and reception circuit, transmission system using the same, electronic device, and serial data transmission method.
This patent grant is currently assigned to ROHM CO., LTD.. The grantee listed for this patent is ROHM CO., LTD.. Invention is credited to Shinichi Saito.
United States Patent |
9,270,443 |
Saito |
February 23, 2016 |
**Please see images for:
( Certificate of Correction ) ** |
Serial data transmission circuit and reception circuit,
transmission system using the same, electronic device, and serial
data transmission method
Abstract
Transmission circuit for transmitting serial data with
superposed clock signal includes encoder to scramble parallel data
of information and apply predetermined coding scheme to generate D
symbols having clock signal embedded therein, and to output
alternately continuous predetermined number of the D symbols and
one of K symbols as synchronization control codes for the
scrambling; and parallel-to-serial converter configured to convert
the D symbols and the K symbols output from the encoder into serial
data, wherein, for each period of the scrambling, the encoder
outputs K symbols, each of which is allocated to one of the first
code indicating beginning of the period of the scrambling, the
second code allocated at equal interval among remaining ones of the
K symbols other than that for the first code, and a third code
allocated among remaining ones of the K symbols other than those
for the first code and the second code.
Inventors: |
Saito; Shinichi (Kyoto,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
ROHM CO., LTD. |
Ukyo-ku, Kyoto |
N/A |
JP |
|
|
Assignee: |
ROHM CO., LTD.
(JP)
|
Family
ID: |
53755728 |
Appl.
No.: |
14/609,924 |
Filed: |
January 30, 2015 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20150222416 A1 |
Aug 6, 2015 |
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Foreign Application Priority Data
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Jan 31, 2014 [JP] |
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2014-017404 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L
7/0054 (20130101); H04L 7/043 (20130101) |
Current International
Class: |
H04L
27/00 (20060101); H04L 7/00 (20060101); H04L
7/04 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2000078027 |
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Mar 2000 |
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JP |
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2007096903 |
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Apr 2007 |
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JP |
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2012120100 |
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Jun 2012 |
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JP |
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Primary Examiner: Bocure; Tesfaldet
Attorney, Agent or Firm: Cantor Colburn LLP
Claims
What is claimed is:
1. A transmission circuit for transmitting serial data with a
superimposed clock signal, comprising: an encoder configured to
scramble parallel data of information to be transmitted and apply a
predetermined coding scheme to generate D symbols having a clock
signal embedded therein, and also configured to output alternately
a continuous predetermined number of the D symbols and one of K
symbols, the K symbols being synchronization control codes for the
scrambling; and a parallel-to-serial converter configured to
convert the D symbols and the K symbols output from the encoder
into serial data, wherein, for each period of the scrambling, the
encoder outputs a plurality of the K symbols, each of which is
allocated to one of a first code, a second code, and a second code,
wherein the first code indicates a beginning of the period of the
scrambling, wherein the second code is allocated at an equal
interval among remaining ones of the K symbols other than that for
the first code; and wherein the third code is allocated among
remaining ones of the K symbols other than those for the first code
and the second code.
2. The transmission circuit of claim 1, wherein the parallel data
comprises pixel data forming image data, and the period of the
scrambling is based on one line of the image data.
3. A reception circuit for receiving serial data with a
superimposed clock signal, wherein the serial data includes D
symbols having a clock signal embedded therein that have been
obtained by scrambling first parallel data of information to be
transmitted and applying a predetermined coding scheme, and also
includes K symbols that are synchronization control codes for the
scrambling, wherein each of the K symbols is arranged at an equal
interval for every predetermined plural number of the D symbols,
wherein, for each period of the scrambling, the serial data
includes a plurality of the K symbols, including, a first code
inserted once for the period of the scrambling; a second code
arranged at an interval shorter than that for the first code; and a
third code arranged at positions other than those for the first
code and the second code, and the reception circuit comprising: a
serial-to-parallel converter configured to convert the serial data
into second parallel data; and a decoder configured to determine
whether the second parallel data is the D symbol or the K symbol,
(i) when the second parallel data is the D symbol, perform decoding
and descrambling of the second parallel data, and (ii) when the
second parallel data is the K symbol, determine what the second
parallel data is among the first to third codes to synchronize the
descrambling with the scrambling in a transmission circuit based on
the determined code.
4. The reception circuit of claim 3, wherein the second parallel
data comprises pixel data forming image data, and the period of the
scrambling is based on one line of the image data.
5. The reception circuit of claim 3, wherein the second parallel
data comprises pixel data forming image data, and, wherein the
reception circuit further comprises: an error detector configured
to determine, based on the second parallel data generated by the
serial-to-parallel converter, whether the second parallel data is
correct or erroneous; a correcting buffer configured to, when it is
determined by the error detector that the second parallel data is
correct, maintain the pixel data included in the second parallel
data; and a correction unit configured to substitute the pixel data
included in the second parallel data determined as being erroneous
by the error detector with a value corresponding to the pixel data
maintained in the correcting buffer.
6. The reception circuit of claim 5, wherein the error detector is
configured to determine whether the second parallel data is correct
or erroneous based on results of the decoding or the descrambling
by the decoder.
7. The reception circuit of claim 5, wherein the first parallel
data before parallel-to-serial conversion in the transmission
circuit comprises at least one bit for error detection, and wherein
the error detector is configured to determine whether the second
parallel data is correct or erroneous based on the at least one bit
for error detection.
8. The reception circuit of claim 5, wherein the first parallel
data before parallel-to-serial conversion comprises a
synchronization signal that is regularly changed over time, and
wherein the error detector is configured to determine whether the
second parallel data is correct or erroneous by comparing the
synchronization signal comprised in the second parallel data with
an expected pattern.
9. The reception circuit of claim 8, further comprising: a
synchronization signal generating unit configured to compare the
synchronization signal with the expected pattern and correct the
synchronization signal based on the expected pattern when the
synchronization signal is different from the expected pattern.
10. A transmission system, comprising: the transmission circuit of
claim 1; and the reception circuit of claim 3.
11. An electronic device comprising the transmission system of
claim 10.
12. A method of transmitting serial data, comprising: in a
transmission circuit, scrambling first parallel data of information
to be transmitted and applying a predetermined coding scheme to
generate D symbols having a clock signal embedded therein; in the
transmission circuit, alternately arranging a predetermined number
of continuous D symbols and a K symbol, the K symbol being a
synchronization control code for the scrambling; and in the
transmission circuit, parallel-to-serial converting the D symbols
and the K symbol into serial data and transmitting the serial data
to a reception circuit; in the reception circuit, converting the
serial data into second parallel data; determining whether the
second parallel data is the D symbol or the K symbol; and in the
reception circuit, (i) when the second parallel data is the D
symbol, decoding and descrambling the second parallel data, (ii)
when the second parallel data is the K symbol, determining what the
second parallel data is among the first to third codes to
synchronize the descrambling with the scrambling in the
transmission circuit based on the determined code, and wherein, for
each period of the scrambling, the transmission circuit arranges a
plurality of the K symbols, the plurality of the K symbols
including, a first code indicating a beginning of the period of the
scrambling; second codes each of which is allocated at an equal
interval to the remaining K symbols other than that for the first
code; and third codes allocated to the remaining K symbols other
than those for the first code and the second codes.
13. The method of claim 12, wherein the second parallel data
comprises pixel data forming image data, and wherein the method
further comprises: in the reception circuit, determining, based on
the second parallel data, whether the second parallel data is
correct or erroneous; in the reception circuit, when it is
determined that the second parallel data is correct, maintaining
the pixel data included in the second parallel data in a correcting
buffer; and substituting the pixel data included in the second
parallel data determined as being erroneous with a value
corresponding to the pixel data maintained in the correcting
buffer.
14. The method of claim 13, wherein the determining whether the
second parallel data is correct or erroneous comprises determining
whether the second parallel data is correct or erroneous based on
results of the decoding or the descrambling.
15. The method of claim 13, wherein the first parallel data before
parallel-to-serial conversion in the transmission circuit comprises
at least one bit for error detection, and wherein the determining
whether the second parallel data is correct or erroneous comprises
determining whether the second parallel data is correct or
erroneous based on the at least one bit for error detection.
16. The method of any one of claim 13, wherein the first parallel
data before parallel-to-serial conversion in the transmission
circuit comprises a synchronization signal that is regularly
changed over time, and wherein the determining whether the second
parallel data is correct or erroneous comprises determining whether
the second parallel data is correct or erroneous by comparing the
synchronization signal comprised in the second parallel data with
an expected pattern.
17. The method of claim 16, further comprising: in the reception
circuit, comparing the synchronization signal with the expected
pattern and correcting the synchronization signal based on the
expected pattern when the synchronization signal is different from
the expected pattern.
Description
CROSS-REFERENCE TO RELATED APPLICATION
This application is based upon and claims the benefit of priority
from Japanese Patent Application No. 2014-017404, filed on Jan. 31,
2014, the entire contents of which are incorporated herein by
reference.
TECHNICAL FIELD
The present disclosure relates to techniques of serial data
transmission using a clock data recovery (CDR) circuit.
BACKGROUND
In order to transmit and receive data between semiconductor
integrated circuits through a small number of data transmission
lines, the techniques of serial data transmission are used. As the
techniques of serial data transmission, a scheme of transmitting
serial data and a clock signal through separate respective
transmission lines and a scheme of superimposing a clock signal on
serial data have been known.
The former scheme, which is also referred to as a clock
synchronization scheme, may be employed, for example, in a low
voltage differential signaling (LVDS) bus, and an inter IC
(I.sup.2C) bus. In this scheme, however, synchronization between
the clock signal and the serial data may be lost due to an
influence of jitter of the clock signal or a difference in
propagation delays between the serial data and the clock signal so
that it is difficult to transmit the data at a high speed exceeding
1 Gbps.
In contrast, the scheme of superimposing the clock signal on the
serial data, in a transmission circuit, the serial data is encoded
such that bits are changed according to a predetermined rule. A
reception circuit reproduces the clock signal embedded in the
serial data. In this sense, this scheme is also referred to as a
CDR (Clock Data Recovery) scheme. In the CDR scheme,
synchronization between the serial data and the clock signal can be
maintained so that a higher transfer rate may be realized.
In order to solve the problem of electromagnetic interference (EMI)
caused in the serial data transmission, a transmitter may scramble
the serial data and randomize the serial data propagating through a
transmission channel, thereby spreading a spectrum in the related
art.
FIG. 1 shows a data format for a conventional serial data
transmission adopting the scrambling. A smallest unit of data is
called 1 word. In case of using an 8B10B coding scheme, 1 word is
10 bits, 8 bits of which are data corresponding to information and
remaining 2 bits of which are redundancy bits for embedding the
clock signal.
Image data (pixel data) may be scrambled and subsequently 8B10B
coded to generate a word called a D symbol. Scramble controlling
codes (K symbols) are respectively arranged at an equal interval
for a plurality of D symbols. For example, each K symbol may be
inserted once every ten words.
The transmission circuit may generate a pseudorandom number
changing at a predetermined cycle (e.g., every one word) and
performs scrambling on the image data with the pseudorandom number.
The K symbols may include a first (initialization) code K0 and a
second code (synchronization code) K1. The initialization code K0
may be inserted one time for each scrambling period (e.g., every
1000 words). The initialization code K0 may indicate the beginning
of generating a pseudorandom number. The remaining K symbols may be
allocated to the synchronization code K1.
The reception circuit may be synchronized with the transmission
circuit by referring to the K symbols so that it generates the same
pseudorandom number as the pseudorandom number generated by the
transmission circuit and descrambles the received data using the
generated pseudorandom number.
Here, if the transmission circuit and the reception circuit lose
synchronization, the pseudorandom numbers generated by the
transmission circuit and the reception circuit are not identical,
and thus, descrambling may not be correctly performed. That is,
when the synchronization is lost in the middle of a scrambling
period, a reception error occurs.
The synchronization code K1 may be included once for every 10
words. Thus, even in a case in which the transmission circuit and
the reception circuit lose synchronization, if a synchronization
shift occurs within the front and rear 5 words, a current correct
word position may be known by normally receiving the next
synchronization code K1 so that the synchronization may be
reestablished and the pseudorandom number may also be returned to a
correct value. However, if the synchronization shift exceeds the
front and rear 5 words, a correct word position may not be restored
in spite of using the synchronization code K1 so that the
synchronization error continues until the next initialization code
K0 is correctly received.
For example, in an electronic device including a display panel, the
serial data transmission may be used in transmitting image data
from a frame memory storing the image data (which includes a video
and a still image) to a driver circuit of the display panel. In a
case where scrambling is performed for each line of image data as a
unit period, when a synchronization error exceeding 10 words occurs
in the middle of data transmission of a certain line, subsequent
image data in that line may not be correctly displayed, which
causes disturbance of an image recognized by a user.
SUMMARY
The present disclosure provides some embodiments of a transmission
technique capable of resuming descrambling, even when a
transmission error occurs, by establishing a synchronous state
between transmission and reception sides within a short time.
According to an aspect of the present disclosure, there is provided
a transmission circuit for transmitting serial data with a
superimposed clock signal, including: an encoder that scrambles
parallel data of information to be transmitted and applies a
predetermined coding scheme to generate D symbols having a clock
signal embedded therein, and outputs alternately a continuous
predetermined number of the D symbols and one of K symbols that are
synchronization control codes for the scrambling; and a
parallel-to-serial converter that converts the D symbols and the K
symbols output from the encoder into serial data. For each period
of the scrambling, the encoder outputs a plurality of the K symbols
each of which is allocated to one of a first code, a second code,
and a third code. The first code indicates a beginning of the
period of the scrambling. The second code is allocated at an equal
interval among remaining ones of the K symbols other than that for
the first code. The third code is allocated to the remaining K
symbols other than those for the first code and the second
codes.
If scrambling is performed, a reception circuit performs
descrambling in synchronization with the transmission circuit based
on the K symbols. According to this aspect, even if a transmission
error occurs and a synchronization error exceeding a period of the
third code occurs, if the synchronization error is within a range
that does not exceed the interval of the second code, a current
position of the serial data may be corrected based on a next second
code without having to receive a next first code. Accordingly, even
if a transmission error occurs, a synchronous state available for
descrambling may be reestablished within a short time.
According to some embodiments, the parallel data may include pixel
data forming image data. The period of the scrambling may be based
on one line of the image data. If the second code is inserted M
times to 1 line, a region in which disturbance of an image occurs
may be suppressed to below 1/M line.
According to another aspect of the present disclosure, there is
provided a reception circuit for receiving serial data with a
superimposed clock signal. The serial data includes D symbols
having a clock signal embedded therein that have been obtained by
scrambling first parallel data of information to be transmitted and
applying a predetermined coding scheme. The serial data also
includes K symbols that are synchronization control codes for the
scrambling and each of which is arranged at an equal interval for
every predetermined number of the D symbols. For each period of the
scrambling, the serial data includes a plurality of the K symbols,
including a first code arranged once for the period of the
scrambling, a second code arranged at an interval shorter than that
for the first code, and a third code arranged at positions other
than those for the first code and the second code. The reception
circuit includes a serial-to-parallel converter that converts the
serial data into second parallel data; and a decoder that
determines whether the second parallel data is the D symbol or the
K symbol, (i) when the second parallel data is the D symbol,
performs decoding and descrambling of the second parallel data, and
(ii) when the second parallel data is the K symbol, determines what
the second parallel data is among the first to third codes to
synchronize the descrambling with the scrambling in a transmission
circuit based on the determined code.
According to this aspect, even if a reception error occurs and a
synchronization error exceeding a period of the third code occurs,
if the synchronization error is within a range that does not exceed
a period of the second code, a current position of the serial data
may be corrected based on a next second code without having to
receive a next first code. Accordingly, a time of the reception
error may be shortened to suppress disturbance of an image
displayed on the display panel.
According to some embodiments, the second parallel data may include
pixel data forming image data. The period of the scrambling may be
based on one line of the image data.
According to some embodiments, the second parallel data may include
pixel data forming image data. The reception circuit further
includes an error detector that determines, based on the second
parallel data generated by the serial-to-parallel converter,
whether the second parallel data is correct or erroneous; a
correcting buffer that, when it is determined by the error detector
that the second parallel data is correct, maintains the pixel data
included in the second parallel data; and a correction unit that
substitutes the pixel data included in the second parallel data
determined as being erroneous by the error detector with a value
corresponding to the pixel data maintained in the correcting
buffer. If a single pixel forming image data is considered, in many
cases, luminance of the pixel is similar to luminance of a nearby
pixel or similar to luminance of the same pixel in a next previous
frame. Thus, in this aspect, the pixel data included in the second
parallel data determined to be correct in the past is maintained as
pixel data representing correct luminance. Accordingly, the pixel
data included in the second parallel data determined to be
erroneous, i.e., pixel data representing erroneous luminance, may
be restored from the pixel data representing the correct luminance
so that disturbance of an image may be suppressed.
According to some embodiments, the error detector determines
whether the second parallel data is correct or erroneous based on
results of the decoding of the decoder.
According to some embodiments, the first parallel data before
parallel-to-serial conversion in the transmission circuit may
include at least one bit for error detection. The error detector
may determine whether the second parallel data is correct or
erroneous based on the at least one bit for error detection.
According to some embodiments, the first parallel data before
parallel-to-serial conversion may include a synchronization signal
that is regularly changed over time. The error detector may
determine whether the second parallel data is correct or erroneous
by comparing the synchronization signal included in the second
parallel data with an expected pattern.
According to some embodiments, the reception circuit may further
include a synchronization signal generating unit that compares the
synchronization signal with the expected pattern and correct the
synchronization signal based on the expected pattern when the
synchronization signal is different from the expected pattern.
Accordingly, even when a transmission error occurs in a
synchronization signal, an image may be correctly displayed.
According to some embodiments, the reception circuit and the
transmission circuit may be integrally integrated on a single
semiconductor substrate. "Integrally Integrated" may include a case
in which all the components of a circuit are formed on a
semiconductor substrate as well as a case in which major components
of a circuit are integrally integrated and resistors, capacitors,
or some other components may be installed outside of the
semiconductor substrate in order to adjust circuit constants. By
integrating the circuits into a single IC, a circuit area may be
reduced and characteristics of a circuit element may also be
uniformly maintained.
According to still another aspect of the present disclosure, there
is provided a transmission system. The transmission system includes
any of the transmission circuits described above and any of the
reception circuits described above.
According to still another aspect of the present disclosure, there
is provided an electronic device. The electronic device includes
the transmission system described above.
Also, arbitrarily combining the foregoing components or converting
the expression of the present disclosure between a method and an
apparatus may also be valid as an aspect of the present
disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a data format for a conventional serial transmission
adopting a scrambling function.
FIG. 2 is a block diagram of a transmission system according to an
embodiment.
FIGS. 3A and 3B are views illustrating arrangements of symbols D
and K generated by an encoder.
FIGS. 4A and 4B are operational waveform views of a conventional
transmission system, and FIG. 4C is an operational waveform view of
the transmission system of FIG. 2.
FIG. 5 is a block diagram of a transmission system according to a
modified example 1.
FIG. 6 is a view illustrating a first correction processing.
FIG. 7 is a block diagram of a transmission system according to a
modified example 2.
FIG. 8 is a perspective view illustrating an electronic device.
FIG. 9 is a flow chart illustrating an example process, which may
be performed in the transmission circuit 20 of FIG. 2 according to
one embodiment.
FIG. 10 is a flow chart illustrating an example process, which may
be performed in the reception circuit 30 of FIG. 2 according to one
embodiment.
DETAILED DESCRIPTION
Embodiments of the present disclosure will now be described with
reference to the drawings. Throughout the drawings, the same or
equivalent components, members, and processes are denoted by the
same reference numerals and a repeated description thereof will be
properly omitted. Also, the disclosed embodiments are merely
examples and do not limit the present disclosure, and any feature
or combination thereof described in the embodiments may not
necessarily be essential to the present disclosure.
In the present disclosure, "a state in which a member A is
connected to a member B" includes not only a case in which the
member A and the member B are physically directly connected but
also a case in which the member A and the member B are indirectly
connected via any other member that does not affect an electrical
connection state thereof.
Similarly, "a state in which a member C is installed between a
member A and a member B" includes not only a case in which the
member A and the member C or the member B and the member C are
directly connected but also a case in which the member A and the
member C or the member B and the member C are indirectly connected
through any other member that does not affect an electrical
connection state therebetween.
FIG. 2 is a block diagram of a transmission system 10 according to
an embodiment. The transmission system 10 may be used in an
electronic device 1 having a display device. The electronic device
1 may include an image processing device 12 and a display device 14
in addition to the transmission system 10. The image processing
device 12 may be a central processing unit (CPU) or a graphics
processing unit (GPU) and may generate image data (including a
still image and a video image) to be displayed on the display
device 14. In many electronic devices 1, the image processing
device 12 and the display device 14 may be arranged to be separated
from one another. The transmission system 10 may be used to
transmit the image data from the image processing device 12 to the
display device 14.
The transmission system 10 includes a transmission circuit 20, a
transmission channel 18, and a reception circuit 30. The
transmission circuit 20 and the reception circuit 30 may convert
pixel data forming the image data into a serial format and perform
high speed serial transmission through the transmission channel 18.
A clock signal may be embedded in the serial data propagated
through a serial lane LS forming the transmission channel 18. In
FIG. 2, only the single serial lane LS is illustrated, but, in some
cases, a plurality of serial lanes may be installed in
parallel.
The pixel data forming the image data (hereinafter, referred to as
"RGB" data) may include luminance data of three R, G, and B color
subpixels included in the corresponding pixel (hereinafter,
referred to as subpixel data or R data, G data, and B data). The
transmission circuit 20 receives the RGB data and a pixel clock
CKPX in synchronization with the RGB data from the image processing
device 12. A period of the pixel clock CKPX is in proportion to a
generation period of the RGB data.
Further, a synchronization signal SYNC generated by the image
processing device 12 may be also received at the transmission
circuit 20, in addition to the RGB data. The synchronization signal
SYNC may include a horizontal synchronization signal HSYNC, a
vertical synchronization signal VSYNC, and a data enable signal DE.
In the case of using K symbols as described later, the data enable
signal DE may be omitted.
The transmission circuit 20 includes a transmission pixel buffer
200, an encoder 204, a parallel-to-serial converter 206, and a
phase locked loop (PLL) circuit 210, and may be a functional
integrated circuit (IC) integrated on a single semiconductor
substrate.
The transmission pixel buffer 200 may latch information, which is
output from the image processing device 12 and to be transmitted to
the display device 14, i.e., the pixel data RGB and the
synchronization signal SYNC, by using the pixel clock CKPX, and
maintains the same. The pixel data RGB and the synchronization
signal SYNC may be stored in the transmission pixel buffer 200 by a
unit of 8 bits.
The encoder 204 may scramble the 8 bit parallel data maintained in
the transmission pixel buffer 200. Further, the encoder 204 may
encode the scrambled data according to a predetermined scheme
(e.g., 8B10B) and adds redundancy bits thereto to embed a clock
signal. The generated data is called a D symbol (or D code).
The transmission pixel buffer 200 may store the pixel data RGB and
the synchronization signal SYNC by a unit of 10 bits. In this case,
10B12B coding may be used.
Also, the encoder 204 may insert K symbols (also referred to as K
codes) as synchronization control codes at an equal interval for
every predetermined number of D symbols. The encoder 204 may output
a continuous predetermined number (p-1) (where p is an integer) of
D symbols and a single K symbol alternately. That is, a period of
the K symbols (K code period Tk) is p words. In this embodiment, it
is assumed that p=10.
The K code is set to be distinguished from the D code. For example,
the D code generated through 8B10B coding or 10B12B coding may be
level-shifted in a ratio of once for a predetermined number of
bits. Thus, the K code may be generated to maintain 1 or 0 over a
number of bits exceeding the predetermined number of bits.
Scrambling will now be described. The encoder 204 may be
initialized at every predetermined number of words q (hereinafter,
referred to as a scrambling period Ts) and may generate a
pseudorandom number (scramble code) changing at every predetermined
number of words r (hereinafter, referred to as a transition period
Tt). Then, the encoder 204 may perform the scrambling on the data
stored in the transmission pixel buffer 200 with the pseudorandom
number. In this embodiment, the scrambling period Ts is set to
q=1000 words. Also, the transition period Tt is set to r=1 word,
but in modified examples, r may be 2 or greater.
In order to generate the pseudorandom number, a linear feedback
shift register (LFSR) may be used. In this case, data within the
register is shifted at every transition period Tt, i.e. at every
one word. The encoder 204 may perform the scrambling by applying an
XOR operation on the pseudorandom number and the parallel data.
Further, there is no particular limitation on scrambling
methods.
FIGS. 3A and 3B are views illustrating arrangements of D symbols
and K symbols generated by the encoder 204. As illustrated in FIG.
3A, a K symbol (K) and a plurality (p-1) of continuous D symbols
are alternately arranged in a scrambling period Ts. In the
scrambling period Ts, m (=q/p) number of K symbols are included. In
this embodiment, m=100.
FIG. 3B illustrates only the K symbols extracted from the data of
FIG. 3A. The m number of K symbols included in the scrambling
period Ts includes the first code (hereinafter, referred to as an
initialization code) K0, the second code (hereinafter, referred to
as a higher synchronization code) K2, and the third code
(hereinafter, referred to as a lower synchronization code) K1,
which are distinguishable from one another.
The initialization code K0 indicates a beginning of the scrambling
period Ts. The higher synchronization code K2 may be allocated
among remaining K symbols, other than that for the initialization
code K0, at an equal interval. The lower synchronization code K1
may be allocated to remaining K symbols, other than those for the
initialization code K0 and the higher synchronization code K2.
The initialization code K0 may be the first K symbol. Each higher
synchronization code K2 may be allocated for every predetermined n
number of K symbols. That is, (1+n.times.j).sup.th K symbol may be
the higher synchronization code K2. Here, j=0, 1, 2, . . . . The
remaining K symbols may be allocated to the lower synchronization
code K1. In this embodiment, it is assumed that n=4.
The first period T1, as the period of the initialization code K0,
is equal to the scrambling period Ts (i.e., q words). The third
period T3, as the period of the lower synchronization code K1, is
equal to the K code period Tk (i.e., p words). The second period
T2, as the period of the higher synchronization code K2, is equal
to Tk.times.n (i.e., p.times.n words).
The PLL circuit 210 multiplies the pixel clock CKPX to generate a
serial clock CKS. The parallel-to-serial converter 206 converts
sequentially parallel-to-serial the D symbols or the K symbols
outputted from the encoder 204 in synchronization with the serial
clock CKS. A differential driver 208 outputs serial data SD to the
serial lane LS.
Next, the reception circuit 30 will be described. The reception
circuit 30 includes a differential receiver 300, a CDR circuit 301,
a serial-to-parallel converter 302, a decoder 306, a reception
pixel buffer 308, and a clock generating unit 310, and may be a
functional IC integrated on a single semiconductor substrate.
The differential receiver 300 may receive the serial data SD and
determines whether each bit is a high level or a low level. The CDR
circuit 301 may monitor output from the differential receiver 300
to extract a clock signal embedded in the serial data SD, and
reproduces a sampling clock CKS.
The serial-to-parallel converter 302 converts the serial data SD
received by the differential receiver 300 into parallel data. An
output of the serial-to-parallel converter 302 is a D symbol or a K
symbol.
The decoder 306 may perform 8B10B decoding on the D symbol. The
decoder 306 has a pseudorandom number generating unit (e.g., the
LFSR) that is the same as that included in the encoder 204. The
decoder 306 may generate the pseudorandom numbers that change in
synchronization with those used in the transmission circuit 20
based on the K symbols and descrambles the D symbols using the
generated pseudorandom numbers. Specifically, when the
initialization code K0 is received, the decoder 306 may initialize
the pseudorandom number, and thereafter, the decoder 306 may change
the pseudorandom number at every one word.
The clock generating unit 310 may generate a pixel clock CKPX
having the same frequency as that of the pixel clock CKPX of the
transmission circuit 20. Processing after the reception pixel
buffer 308 may be performed in synchronization with the pixel clock
CKPX.
The reception pixel buffer 308 may store the synchronization signal
SYNC and the pixel data RGB decoded by the decoder 306. This
information may be sequentially output to the display device
14.
The configuration of the transmission system 10 has been described.
Next, operations of the transmission system 10 will be
described.
FIGS. 4A and 4B are operational waveform views of a conventional
transmission system. FIG. 4C is an operational waveform view of the
transmission system 10 of FIG. 2.
The problem of the conventional transmission system will be
described again with reference to FIGS. 4A and 4B. As mentioned
above, the initialization code K0 is allocated at the beginning of
the scrambling period and thereafter, the synchronization code K1
is allocated. X.sub.0-9 and X.sub.10-19, for example, denote the
pseudorandom numbers TX and RX respectively generated by the
encoder of the transmission circuit and the decoder of the
reception circuit. When the initialization code K0 is received, the
pseudorandom number is initialized to X.sub.0 and then, the
pseudorandom number transitions to X.sub.1, X.sub.2, X.sub.3 . . .
at every one word. When the K symbol is correctly received, the
pseudorandom number X of the reception side is identical to that of
the transmission side.
However, when a transmission error occurs in a certain cycle t0 so
that receiving of the synchronization code K1 fails, the scrambler
of the transmission circuit and the descrambler of the reception
circuit lose synchronization, which causes inconsistency of the
pseudorandom numbers X. Thus, a decoding error occurs.
FIG. 4A illustrates a state in which a transmission error for a
shorter time than the K code period Tk, occurs between 60 to 70
words. In this case, the decoding error continues from a time t0 at
which the transmission error occurs to a time t1 at which the
synchronization code K1 is correctly received next. After the time
t1 at which the synchronization code K1 is correctly received, data
may be correctly descrambled.
FIG. 4B illustrates a state in which a synchronization error for a
longer time than the K code period Tk, occurs between 60 to 80
words to cause the failure of receiving the synchronization code
K1. Once it fails to receive the synchronization code K1, the
reception circuit does not know a position of serial data until the
next initialization code K0 is correctly received. That is, a
decoding error continues for a long period of time.
Advantages of the transmission system 10 of FIG. 2 will be
described with reference to FIG. 4C. When a transmission error
occurs at a certain time t0 and thus the transmission and reception
circuits lose synchronization, a decoding error occurs. Then, a
higher synchronization code K2 is transmitted from the transmission
circuit 20 at a time t1 and the reception circuit 30 correctly
receives it. As described above, assuming a case where the
initialization code K0 is allocated for the i.sup.th and the higher
synchronization code K2 is allocated once at every n number of K
symbols, the higher synchronization code K2 is to be allocated for
a (i+n.times.j).sup.th K symbol, i.e., for a
((i+n.times.j).times.p).sup.th word. As such, since the reception
circuit 30 can find a position of the higher synchronization code
K2 in the serial data, the reception circuit 30 may correct the
current position of the serial data based on the higher
synchronization code K2 and restore the pseudorandom number to a
correct value X.sub.40. Accordingly, descrambling may be performed
correctly after the time t1. The operation of the transmission
system 10 has been described.
According to the transmission system 10 of the embodiment, by
allocating the higher synchronization code K2 at a frequency higher
than (a shorter interval) that of the initialization code K0, in
the case of a transmission error that is shorter than the period T2
of the higher synchronization code K2, a continuation time of a
decoding error caused by the transmission error may be shortened to
be within the period of the higher synchronization code K2.
Accordingly, disturbance of an image recognized by a user may be
prevented.
FIG. 9 is a flow chart illustrating an example process for
transmitting serial data, which may be performed in the
transmission circuit 20 of FIG. 2 according to one embodiment.
As illustrated in FIG. 9, parallel data of information to be
transmitted is scrambled at the transmission circuit (S902). A
predetermined coding scheme is applied to the scrambled data to
generate D symbols having a clock signal embedded therein (S904).
For a period of the scrambling, K symbols, each of which is a
synchronization control code for the scrambling, and D symbols are
outputted in a manner that a continuous predetermined number of the
D symbols are outputted after one of the K symbols is outputted
(S906). A first code may be allocated to one of the K symbols to
indicate a beginning of the period of the scrambling. A second code
may be allocated among remaining ones of the K symbols other than
that for the first code. A third code may be allocated among
remaining ones of the K symbols other than those for the first code
and the second codes. Then, the K symbols and the D symbols
outputted are parallel-to-serial converted into serial data to be
transmitted to a reception circuit (S908).
FIG. 10 is a flow chart illustrating an example process for
receiving serial data, which may be performed in the reception
circuit 30 of FIG. 2 according to one embodiment.
As depicted, the received serial data is converted into parallel
data (S1002). Then, it is determined whether the second parallel
data is the D symbol or the K symbol (S1004). When it is determined
that the parallel data is the K symbol, it is determined what the
parallel data is among the first to third codes (S1006). Then,
based on the determined code, a pseudorandom number is generated
(S1008). When it is deter pined that the parallel data is the D
symbol, the parallel data is decoded and descrambled in
synchronization with the transmission circuit based on the
pseudorandom number (S1010).
The present disclosure has been described based on the embodiment.
The embodiment is illustrative and there may be various modified
examples of each component, each process, and a combination
thereof. Hereinafter, such modified examples will be described.
MODIFIED EXAMPLE 1
FIG. 5 is a block diagram of a transmission system 10a according to
a modified example 1. A transmission circuit 20a is the same as the
transmission circuit 20 of FIG. 2. Serial data generated according
to 8B10B or 10B12B coding may have a format allowing for detection
of a transmission error by a reception circuit 30a.
The reception circuit 30a includes an error detector 312, a
synchronization signal generating unit 314, a correcting buffer
316, and an error correcting unit 318, in addition to the reception
circuit 30 of FIG. 2.
The error detector 312 may determine whether there is a
transmission error based on parallel data generated by the
serial-to-parallel converter 302. When a transmission error is
detected, the error detector 312 may determine that the parallel
data is not correct. When a transmission error is not detected, the
error detector 312 may determine that the parallel data is correct.
As described above, in the case of using the 8B10B or 10B12B
coding, a pattern to be taken by the D symbols has already been
set. Further, a pattern to be taken by the K symbols has also
already been set. Thus, if received data is not identical to any
pattern, it may be determined as the transmission error (decoding
error).
Also, as described above, the transmission circuit 20a scrambles
the D symbols. Thus, if an error is detected during the
descrambling by the decoder 306, the error detector 312 may
determine that there is a transmission error (scrambling
error).
The synchronization signal generating unit 314 may receive the
synchronization signal SYNC and outputs the synchronization signal
SYNC to the display device 14. Here, the synchronization signal
SYNC, specifically, the vertical synchronization signal VSYNC, the
horizontal synchronization signal HSYNC, or the enable signal DE is
regularly changed over time. Thus, the reception circuit 30 may
estimate a correct value (an expected pattern) to be taken by the
synchronization signal SYNC with respect to each pixel. Thus, the
error detector 312 may determine whether the respective parallel
data is correct or erroneous by comparing the synchronization
signal SYNC with the expected pattern.
For example, in relation to a certain synchronization signal SYNC,
consider four continuous pixels. It may not happen that the
synchronization signal SYNC changes twice within the four
continuous pixels. Thus, by monitoring a level change (edge) of the
synchronization signal SYNC, if two or more level changes are
detected within the four continuous pixels, it may be determined as
a transmission error (synchronization error).
Further, the synchronization signal generating unit 314 may correct
the synchronization signal SYNC based on the result of comparing
the synchronization signal SYNC and the expected pattern. That is,
when the received synchronization signal SYNC is not consistent
with the expected pattern, the synchronization signal generating
unit 314 may correct the synchronization signal SYNC based on the
expected pattern. Accordingly, even when a transmission error
occurs in the synchronization signal SYNC, a correct
synchronization signal SYNC may be reproduced to correctly display
an image.
When the parallel data is determined to be correct by the error
detector 312, the correcting buffer 316 maintains the pixel data
RGB included in the corresponding parallel data. For example, the
correcting buffer 316 may be a line buffer for maintaining pixel
data of 1 line portion running back from the currently received
pixel. For example, if the display device 14 has a display region
of 640.times.480 pixels, the line buffer may maintain pixel data
RGB of an immediately previous continuous 640-pixel portion. In a
case where incorrect pixel data RGB is generated for a certain
pixel, correct pixel data RGB for a nearby pixel may be stored in
the line buffer.
The error correcting unit 318 may substitute the pixel data RGB
included in the parallel data that is determined to be erroneous by
the error detector 312 with a value corresponding to pixel data
RGB' stored in the correcting buffer 316.
The corrected RGB data is supplied to the display device 14 at the
next stage.
So far, the configuration of the transmission system 10a has been
described.
Subsequently, an operation thereof will be described.
As described above, serial data SD1 to SD4 transmitted via the
transmission channel 18 has a format allowing for the error
detection by the reception circuit 30. Further, the error detector
312 may detect a transmission error based on an error detection
code EDB.
The pixel data stored in the correcting buffer 316 may be updated
depending on whether the error detector 312 detects an error or
not. The error correcting unit 318 may select the pixel data RGB'
stored in the correcting buffer 316 if a transmission error is
detected or alternatively may select the pixel data RGB' of the
reception pixel buffer 308 if a transmission error is not detected
so that a value corresponding to the selected pixel data is output
to the display device 14.
Processing performed by the error correcting unit 318 will be
described.
(First Correction Processing)
FIG. 6 is a view illustrating first correction processing. For
example, the error correcting unit 318 substitutes the pixel data
RGB included in the parallel data determined to be erroneous by the
error detector 312 with the pixel data RGB' stored in the
correcting buffer 316. In FIG. 6, coordinates (X, Y) denote
currently received pixels. The pixel data RGB' is pixel data in the
vicinity of the error-detected pixel. The nearby pixel may be a
pixel PH adjacent in a horizontal direction (a leftward direction)
or a pixel PV adjacent in a vertical direction (an upward
direction) of one previous line.
Further, with respect to pixels of a first row, there is no line
adjacent in an upward direction. Thus, the correcting buffer 316
may additionally maintain pixel data of the first row of the next
previous frame. Accordingly, it is also possible to achieve
correction based on the past frame data FR.
(Second Processing)
The error correcting unit 318 may substitute the pixel data RGB
included in the parallel data determined to be erroneous by the
error detector 312 with a value calculated from the pixel data RGB'
stored in the correcting buffer 316. For example, a value obtained
by averaging a plurality of pixel data RGB' in the vicinity of the
current pixel (X, Y) may be used.
(Third Processing)
The correcting buffer 316 may maintain pixel data for one frame
portion, rather than one line portion. In this case, the correcting
buffer 316 may correct the currently erroneous data with reference
to pixel data of the same pixel in the next previous frame.
So far, the operation of the transmission system 10a has been
described. If a pixel forming image data is considered, in many
cases, luminance of the pixel may be similar to luminance of a
nearby pixel or similar to luminance of the same pixel in next
previous frame. The correcting buffer 316 maintains pixel data
included in the parallel data determined to be correct in the past,
as pixel data representing correct luminance. Accordingly, the
pixel data included in the parallel data determined to be
erroneous, i.e., pixel data representing erroneous luminance, may
be restored from the pixel data representing the correct luminance
so that disturbance of an image may be suppressed.
MODIFIED EXAMPLE 2
FIG. 7 is a block diagram of a transmission system 10b according to
a modified example 2. A transmission circuit 20b of FIG. 7 includes
an error detection code generating unit 202 in addition of the
transmission circuit 20a of FIG. 5.
The error detection code generating unit 202 may perform signal
processing required to allow a reception circuit 30b to detect a
transmission error. Specifically, the error detection code
generating unit 202 may generate an error detection bit (EDB)
embedded in serial data transmitted via the transmission channel
18. An error detection may be performed by using a known technique
and is not particularly limited in the present disclosure. For
example, a check sum data scheme, a parity bit scheme, a block
check character (BCC) scheme, or a cyclic redundancy check (CRC)
may be used. The error detection code EDB may be included in the D
symbol.
Subsequently, the reception circuit 30b will be described. In the
reception circuit 30b of FIG. 7, the error detector 312 may
determine whether there is a transmission error or not with
reference to the error detection code EDB stored in the reception
pixel buffer 308. The error detector 312 may determine that
parallel data is not correct if a transmission error is detected
and alternatively, may determine that the parallel data is correct
if a transmission error is not detected.
According to this modified example, a transmission error may be
detected based on an error detection code EDB, in addition to or in
the place of a decoding error, a descrambling error, and a
synchronization error, and image data may be corrected.
MODIFIED EXAMPLE 3
Among the higher synchronization codes K2, some may be selected at
equal intervals to have a code K2a that is set to a value
distinguishable from the other higher synchronization code K2b. In
this case, when a transmission error for a time that is longer than
the period of the code K2b and shorter than the period of code K2a
occurs, a duration of a decoding error may be set to be shorter
than the period of K2a.
MODIFIED EXAMPLE 4
In the embodiments, transmitting the image data has been described.
However the present disclosure is not limited thereto and may also
be applied to any other types of data transmission.
Finally, the purpose of the transmission system 10 will be
described. FIG. 8 is a perspective view illustrating an electronic
device. The electronic device 500 of FIG. 8 may be a notebook PC, a
tablet terminal, a smartphone, a portable game device, or an audio
player. The electronic device 500 may include an image processing
device 12, a transmission system 10, and a display device 14, all
of which are installed in a case 502. The display device 14,
specifically, may include a display panel 504 and a driving circuit
506. The driving circuit 506 may include a timing controller 506a,
a gate driver 506b, and a data driver 506c.
Alternatively, the transmission system 10 may be used to transmit
data to a display installed in a car navigation system or a console
panel for a vehicle. In a vehicle, since strong tolerance to noise
is required, the transmission system 10 may be appropriately used.
Further, the transmission system 10 may be used, for example, for a
Pachinko game machine. In the Pachinko game machine, when a ball is
hit by a nail, noise is generated to cause a transmission error.
The use of the transmission system 10 may reduce image
disturbance.
According to the present disclosure, even if a transmission error
occurs, a synchronous state available for descrambling may be
reestablished within a short time.
While certain embodiments have been described, these embodiments
have been presented by way of example only, and are not intended to
limit the scope of the disclosures. Indeed, the novel methods and
apparatuses described herein may be embodied in a variety of other
forms; furthermore, various omissions, substitutions and changes in
the form of the embodiments described herein may be made without
departing from the spirit of the disclosures. The accompanying
claims and their equivalents are intended to cover such forms or
modifications as would fall within the scope and spirit of the
disclosures.
* * * * *