U.S. patent application number 12/852212 was filed with the patent office on 2011-03-03 for method of and device for detecting cable connection.
This patent application is currently assigned to Renesas Technology Corp.. Invention is credited to Kenji KUBO, Hiroyuki Maemura, Wataru Tanaka.
Application Number | 20110055615 12/852212 |
Document ID | / |
Family ID | 18970959 |
Filed Date | 2011-03-03 |
United States Patent
Application |
20110055615 |
Kind Code |
A1 |
KUBO; Kenji ; et
al. |
March 3, 2011 |
METHOD OF AND DEVICE FOR DETECTING CABLE CONNECTION
Abstract
The detector includes a plug for connecting a personal computer
through a cable, a battery power supply which provides a constant
power supply, and an MCU which receives a specific potential from
the personal computer when the latter is connected.
Inventors: |
KUBO; Kenji; (Hyogo, JP)
; Tanaka; Wataru; (Hyogo, JP) ; Maemura;
Hiroyuki; (Itami-shi, JP) |
Assignee: |
Renesas Technology Corp.
Mitsubishi Electric System LSI Design Corporation
|
Family ID: |
18970959 |
Appl. No.: |
12/852212 |
Filed: |
August 6, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11826371 |
Jul 13, 2007 |
7797557 |
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12852212 |
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|
11447898 |
Jun 7, 2006 |
7334151 |
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11826371 |
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09971674 |
Oct 9, 2001 |
7082545 |
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11447898 |
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Current U.S.
Class: |
713/340 |
Current CPC
Class: |
Y02D 10/00 20180101;
G06F 13/4282 20130101; G06F 13/4081 20130101; Y02D 10/151 20180101;
G06F 13/4072 20130101; G06F 1/266 20130101; Y02D 10/14
20180101 |
Class at
Publication: |
713/340 |
International
Class: |
G06F 1/26 20060101
G06F001/26 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 19, 2001 |
JP |
2001-121010 |
Claims
1. A USB device comprising: a central processing unit; a USB
function circuit; a connection detection circuit; a battery; and
terminals that couple with a host system, wherein the terminals
includes that two are data terminals, a reference voltage terminal,
and a power supply voltage terminal, wherein the battery supplies
an operation voltage for the central processing unit, the
connection detection circuit detects a voltage level of the power
supply voltage terminal and notifies the central processing unit of
a detection result, and the central processing unit determines
whether to issue an enable signal to the USB function circuit in
accordance with detection result.
2. The USB device according to claim 1, wherein the connection
detection circuit issues a first level signal based on the
detection result when the voltage level of the power supply voltage
terminal is lower than a first voltage, and issues a second level
signal when the voltage level of the power supply voltage terminal
is higher than the first voltage, and the central processing unit
issues the enable signal in response to receiving the second level
signal.
3. The USB device according to claim 2, wherein the USB function
circuit is in an active mode to perform a communication with the
host system when an enable signal is received from the central
processing unit, and is in a low consumption mode when the enable
signal is not received from the central processing unit.
4. The USB device according to claim 2, wherein the battery is in a
recharging mode using the power supply from the power supply
voltage terminal when detecting the power supplied from the power
supply voltage terminal.
5. A USB device comprising: a central processing unit; an USB
function circuit; a connection detection circuit; a battery; and
terminals the couple with a host system, wherein the terminals
include two data terminals, a reference voltage terminal, and a
power supply voltage terminal, wherein the battery supplies an
operation voltage to the central processing unit, wherein the
connection detection circuit includes an oscillator power supplied
from the power supply voltage terminal and a counter, and issues a
detection signal to the central processing unit in accordance with
count up of the oscillator oscillation by the counter, and wherein
the central processing unit determines whether to issue an enable
signal to the USB function circuit in accordance with the detection
signal of the connection detection circuit.
6. The USB device according to claim 5, wherein the oscillation of
the oscillator is used for the operation clock of the USB function
circuit.
Description
[0001] This application is a divisional of application Ser. No.
11/447,898, filed Jun. 7, 2006, which is a divisional of
application Ser. No. 09/971,674, filed Oct. 9, 2001.
FIELD OF THE INVENTION
[0002] The present invention relates to a method of and device for
detecting wire connection between a personal computer and a
peripheral device by the use of the technology of Universal Serial
Bus ("USB").
BACKGROUND OF THE INVENTION
[0003] FIG. 6 is a block diagram showing a connection between the
personal computer 1007 and the conventional detector 1001. The
personal computer 1007 comprises the root hub 1005 and the plug
1004. The root hub 1005 is a host for communication using the USB.
The root hub 1005 and the plug 1004 are connected through the power
line VBUS and the resistance R2. Electric potential VBUS is
supplied to the peripheral device from the personal computer
through a power line.
[0004] The detector 1001 comprises the level conversion and
protection circuit 1002, MCU 1003, plug 1009, and the resistance
R1. The MCU 1003 and the plug 1009 are connected through the USB
communication line transmitting electrical potential for a
differential signal of a D+ voltage level, and the USB
communication line transmitting electrical potential for a
differential signal of a D- voltage level. The resistance R1 is
connected between the MPU 1003 and the USB communication line
transmitting D- electrical potential. The resistance R1 transmits
an output VREG of a regulator built in the MCU 1003. The plug 1004
of the personal computer 1007 and the plug 1009 of the detector
1001 are connected through the cable 1006.
[0005] Potential VBUS from the personal computer 1007 is applied to
the level conversion and protection circuit 1002 through the plugs
1004 and 1009. When the potential VBUS is received, the level
conversion and protection circuit 1002 outputs the VBUS detection
signal to the MCU 1003.
[0006] In the conventional detector 1001 the level conversion and
protection circuit 1002 is provided outside the MCU 1003. Thus,
reception of potential VBUS is detected in this level conversion
and protection circuit 1002 that is an external circuit with
respect to the MPU 1003. The MCU 1003 detects connection of the
detector 1001 and the personal computer 1007 based on the VBUS
detection signal output by the level conversion and protection
circuit 1002. Thus, in the conventional detector 1001 the level
conversion and protection circuit 1002 is required and therefore it
is difficult to reduce the size of the circuit.
[0007] Some times the detector is provided with a built in battery
power supply and this battery is charged using the potential
received from the personal computer. However, in such a detector it
is difficult to perform fine detection of the connection,
therefore, more circuitry is required to be provided. Therefore,
there is a problem that it is difficult to reduce the size of the
circuit.
SUMMARY OF THE INVENTION
[0008] It is an object of this invention to provide an intelligent
and small-sized detector that consumes less power.
[0009] The detector according to one aspect of this invention
comprises a plug for connecting the detector to the personal
computer through a cable; a battery power supply which outputs a
predetermined constant electrical potential; and a Micro Control
Unit which receives a specific electrical potential from the
personal computer through the plug and cable, and receives the
constant electrical potential from the battery power supply.
[0010] The detector according to another aspect of this invention
comprises a plug for connecting the detector to the personal
computer through a cable; a battery power supply which outputs a
predetermined constant electrical potential; an oscillator which
outputs an oscillation signal; and a Micro Control Unit which
receives a specific electrical potential from the personal computer
through the plug and cable, receives the constant electrical
potential from the battery power supply, and receives the
oscillation signal from the oscillator.
[0011] Other objects and features of this invention will become
apparent from the following description with reference to the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a block diagram of a detector according to a first
embodiment;
[0013] FIG. 2 is a block diagram of a detector according to a
second embodiment;
[0014] FIG. 3 is a block diagram of a detector according to a third
embodiment;
[0015] FIG. 4 is a block diagram of a detector according to a
fourth embodiment;
[0016] FIG. 5 is a block diagram of a detector according to a fifth
embodiment; and
[0017] FIG. 6 is a block diagram showing a connection between 10 a
personal computer and a conventional detector.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] Embodiments of a detector according to the present invention
will be explained below with reference to the accompanying
drawings.
[0019] FIG. 1 is a block diagram of the detector 1 according to a
first embodiment of the present invention. The detector 1 comprises
the MCU 3, the battery power supply 7, and the plug 9. The battery
power supply 7 supplies a predetermined 20 constant electrical
potential to the MCU 3. The plug 9 supplies a specific electrical
potential to the MCU 3.
[0020] The MCU 3 comprises the USB function circuit 5, the CPU and
peripheral circuit 6, and the detection circuit 8. Moreover, the
MCU 3 comprises a VCC terminal for input of a VCC level signal from
the battery power supply 7, VSS terminal which is connected to the
plug 9 for transmission of a standard level VSS (usually, earth
electrical potential, and hereinafter, called as VSS), D+ terminal
which is connected to the plug 9 for transmission of a D+ electric
level, and a D- terminal which is connected to the plug 9 for
transmission of a D- electric level.
[0021] The MCU 3 comprises a VREG terminal for transmission of
output VREG of a regulator built in the USB function circuit 5, and
a VBUS terminal which is connected to the plug 9 for transmission
of VBUS (electrical potential supplied form the personal
computer).
[0022] The USB function circuit 5 is connected to the VCC terminal,
VSS terminal, D+ terminal, D- terminal, VREG terminal, and the VBUS
terminal. The CPU and peripheral circuit 6 is connected to the VCC
and VSS terminals. The CPU and peripheral circuit 6 performs on-off
control of the USB function circuit 5 based on the output of the
detection circuit 8. The detection circuit 8 is connected to the
VBUS terminal, and the CPU and peripheral circuit 6. The resistance
R1 whose one terminal is connected to the VREG terminal, and the
other terminal is connected to a USB communication line for
transmission of the D- electrical potential is provided. The D-
electrical potential is pulled up by the resistance R1 at the VREG
electrical potential in the case of low rate USB communication.
[0023] Although not shown here, the detector 1 is connected to a
personal computer through the plug 9, cable, and a plug in the
personal computer is the same manner as explained with reference to
the conventional detector.
[0024] The D- electrical potential is pulled up to VREG X
(R2/(R1+R2)) V and the D+ electrical potential is pulled down by
the resistance R2, as there is no output by the resistance R1 and
the resistance R2 of the personal computer together with the MCU 3
and the root hub of the personal computer in the case of no
communication.
[0025] Operations of the detector 1 will be described below. When
the cable for connecting the detector 1 and the personal computer
is connected to the plug 9, potential VBUS which is received from
the personal computer is applied to the USB function circuit 5 and
the detection circuit 8.
[0026] The detection circuit 8 supplies the potential VBUS to the
CPU and peripheral circuit 6. The detection circuit 8 monitors the
voltage level of VBUS supplied through the cable. The CPU and
peripheral circuit 6 outputs an Enable signal for ON operation of
the USB function circuit 5 so as to perform USB communication.
[0027] The USB function circuit 5 after the ON operation outputs
the VREG electrical potential of the output of the built-in
regulator. The VREG electrical potential is applied to the D-
terminal while the D- electrical potential of the USB communication
line is pulled up by the resistance R1.
[0028] The detection circuit 8 outputs a signal having a low
logical level ("L") when the potential VBUS is Hi-Z and outputs a
signal having high logical level ("H") when the potential VBUS is
the specific electrical potential (for example, 5 V) to the CPU and
peripheral circuit 6. In other words, the detection circuit 8 shall
output a "L" signal when the detector and the personal computer are
not connected to each other, because, in this case the potential
VBUS will be equal to Hi-Z. On the other hand, the detection
circuit 8 shall output a "H" signal when the detector and the
personal computer are connected to each other, because, in this
case the potential VBUS will be equal to the specific electrical
potential.
[0029] Thus, whether the detector and the personal computer are
connected to each other can be detected by the CPU and peripheral
circuit 6 based on the changes in the voltage level of VBUS
supplied from the detection circuit 8. Accordingly, the MCU 3
functions as a communication controller using the USB between the
detector 1 and the personal computer.
[0030] According to the first embodiment, more intelligent
connection detection using the MCU, compared with that of a
conventional detector, may be realized by provision of the MCU
provided with the detection circuit.
[0031] Moreover, the MCU has an advantage that the MCU eliminate a
special circuit, which has been conventionally required for
detection, as the MCU may have a control function as a peripheral
device (not shown).
[0032] When the detector 1 and the personal computer are not
connected to each other, the peripheral device is activated based
on the built in battery power supply. In this case, the potential
VBUS is not input into the USB function circuit. The USB function
circuit may be made to stop its operation when the potential VBUS
is not received, which shall lead to reduced power consumption. The
USB function circuit may be made to restart its operation when the
detector and the personal computer are once more connected to each
other. Moreover, the MPU 3 may be made to charge the battery power
supply using the potential VBUS.
[0033] FIG. 2 is a block diagram of a detector 11 according to a
second embodiment of the present invention. The detector 11
comprises MCU 13, battery power supply 17 for supplying of
predetermined electrical potential to the MCU 13, and the plug 19
transmitting specific electrical potential to the MCU 13.
[0034] The MCU 13 comprises the USB function circuit 15, CPU and
peripheral circuit 16, and the A-D converter 18. Moreover, the MCU
13 comprises a VCC terminal for input of a VCC level signal from
the battery power supply 17, VSS terminal which is connected to the
plug 19 for transmission of a standard level VSS, D+ terminal which
is connected to the plug 19 for transmission of a D+ electric
level; and a D- terminal which is connected to the plug 19 for
transmission of a D- electric level. The MCU 13 also includes a
VREG terminal for transmission of an output VREG of a regulator
built in the USB function circuit 15 and a VBUS terminal which is
connected to the plug 19 for transmission of VBUS (electrical
potential supplied from the personal computer).
[0035] The USB function circuit 15 is connected to the VCC
terminal, VSS terminal, D+ terminal, D- terminal, VREG terminal,
and the VBUS terminal. The A-D converter 18 is connected to the VCC
terminal, VSS terminal, and the D- terminal. The A-D converter 18
performs conversion of the D- electrical potential to a digital
value for transmission to the CPU and peripheral circuit 16. The
CPU and peripheral circuit 16 is connected to the VCC and VSS
terminals. The CPU and peripheral circuit 16 performs on-off
control of the USB function circuit 15 based on the output of the
A-D converter 18. The resistance R1 whose one terminal is connected
to the VREG terminal, and the other terminal to a USB communication
line for transmission of the D- electrical potential is provided.
The D- electrical potential is pulled up at the VREG electrical
potential in the case of low rate USB communication.
[0036] Although not shown here, the detector 11 is connected to a
personal computer through the plug 19, cable, and a plug in the
personal computer is the same manner as explained with reference to
the conventional detector.
[0037] Moreover, the D- electrical potential is pulled up to VREGX
(R2/(R1+R2)) V and the D+ electrical potential is pulled down by
the resistance R2, as there is no output by the resistance R1 and
the resistance R2 of the personal computer together with the MCU 13
and the root hub of the personal computer in the case of no
communication.
[0038] The detector 11 operates as follows. The D- electrical
potential of the USB communication line is divided by the
resistance R1 and the resistance R2 provided in the personal
computer, in a state the cable is connected to the plug 19 and
there is no communication.
[0039] The divided electrical potential is input to the A-D
converter 18 as an A-D input. The A-D converter 18 outputs the VBUS
detection signal to the CPU and peripheral circuit 16.
[0040] The CPU and peripheral circuit 16 outputs the Enable signal
to the USB function circuit 15 to perform on-off operation of the
USB function circuit 15, and the USB function circuit 15 outputs
the output VREG of the built-in regulator.
[0041] The VREG electrical potential is transmitted to the D-
terminal while the D- electrical potential of the USB communication
line is pulled up by the resistance R1.
[0042] When the detector 11 and the personal computer are not
connected to each other, the D- electrical potential becomes equal
to the output VREG of the regulator. Accordingly, whether the
detector and the personal computer are connected to each other can
be detected based on the detection of the difference in the D-
electrical potential between the connection state of the cable and
the non-connection state of the cable. That is, the difference in
the digital values caused by the connection/non-connection states
of the cable may be used as detection unit.
[0043] According to the second embodiment, the similar advantages
to those of the first embodiment may be expected by provision of
the MCU comprising the A-D converter, and, if the A-D converter is
essentially required as a function of a personal computer
peripheral device, common use of the converter may be
advantageously realized.
[0044] FIG. 3 is a block diagram of a detector 31 according to a
third embodiment of the present invention. The detector 31
comprises the MCU 33, battery power supply 37 for supplying of
predetermined electrical potential to the MCU 33, and the plug 39
transmitting specific electrical potential to the MCU 33.
[0045] The MCU 33 comprises the USB function circuit 35, CPU and
peripheral circuit 36, and the ring oscillator 38. Furthermore, the
MCU 33 comprises a VCC terminal for input of a VCC level signal
from the battery power supply 37, VSS terminal which is connected
to the plug 39 for transmission of a standard level VSS, D+
terminal which is connected to the plug 39 for transmission of a D+
electric level, and a D- terminal which is connected to the plug 39
for transmission of a D- electric level. The MCU 33 also includes a
VREG terminal for transmission of output VREG of a regulator built
in the USB function circuit 35, and a VBUS terminal which is
connected to the plug 39 for transmission of VBUS (electrical
potential supplied from the personal computer).
[0046] The USB function circuit 35 is connected to the VSS
terminal, VSS terminal, D+ terminal, D- terminal, VREG terminal,
and the VBUS terminal. The CPU and peripheral circuit 36 is
connected to the VCC and VSS terminals. The CPU and peripheral
circuit 36 performs on-off control of the USB function circuit 35
based on the output of the ring oscillator 38. The ring oscillator
38 is connected to the VBUS and VSS terminals.
[0047] The resistance R1 whose one terminal is connected to the
VREG terminal and the other terminal is connected to a USB
communication line for transmission of the D- electrical potential
is provided. The resistance R1 pulls up the D- electrical potential
at the VREG electrical potential in the case of low rate USB
communication.
[0048] Although not shown here, the detector 31 is connected to a
personal computer through the plug 39, cable, and a plug in the
personal computer is the same manner as explained with reference to
the conventional detector.
[0049] Moreover, the D- electrical potential is pulled up to VREGX
(R2/(R1+R2)) V and the D+ electrical potential is pulled down by
the resistance R2, as there is no output by the resistance R1 and
the resistance R2 of the personal computer together with the MCU 33
and the root hub of the personal computer in the case of no
communication.
[0050] The detector 31 operates as follows. Potential VBUS
functions as a power supply of the ring oscillator 38 for
oscillation in a state where the cable is connected to the plug 39.
The ring oscillator 38 outputs the VBUS detection signal to the CPU
and peripheral circuit 36. The CPU and peripheral circuit 36
outputs the Enable signal to the USB function circuit 35, and the
USB function circuit 35 outputs the output VREG of the built-in
regulator.
[0051] When the detector 31 and the personal computer are not
connected to each other, the ring oscillator 38 does not oscillate.
Accordingly, whether the detector 31 and the personal computer are
connected to each other can be detected based on monitoring of the
difference in the oscillation output of the ring oscillator 38
between under a connection state and under a non-connection state
of the cable.
[0052] According to the third embodiment, the similar advantages to
those of the first embodiment may be expected by provision of the
MCU comprising the ring oscillator.
[0053] FIG. 4 is a block diagram of a detector 51 according to a
fourth embodiment of the present invention. The detector 51
comprises the MCU 53, battery power supply 57 for supplying of
predetermined electrical potential to the MCU 53, plug 59
transmitting specific electrical potential to the MCU 53, and the
oscillator (for example, ceramic or crystal-oscillation circuit,
and, hereinafter, called as an oscillator) 61 for input/output of
an oscillation signal to/from the MCU 53.
[0054] The MCU 53 comprises the USB function circuit 55, CPU and
peripheral circuit 56, oscillation circuit 58, and the counter 60
for counting of the oscillation output from the oscillation circuit
58. Furthermore, the MCU 53 comprises a VCC terminal for input of a
VCC level signal from the battery power supply 57, D+ terminal
which is connected to the plug 59 for transmission of a D+ electric
level, and a D- terminal which is connected to the plug 59 for
transmission of a D- electric level. The MCU 53 also comprises a
VREG terminal for transmission of an output VREG of a regulator
built in the USB function circuit 55, and a VBUS terminal which is
connected to the plug 59 for transmission of VBUS (electrical
potential supplied from the personal computer) In addition, the MCU
53 comprises a XIN terminal, and a XOUT terminal for transmission
of an oscillation signal which is input to the oscillation circuit
58 from the oscillator 61 and vice versa.
[0055] The USB function circuit 55 is connected to the D+ terminal,
D- terminal, VREG terminal, and the VBUS terminal. The oscillation
circuit 58 is connected to the VBUS terminal, XIN terminal, and the
XOUT terminal. The oscillation circuit 58 performs transmission of
the oscillation output to the counter 60. The CPU and peripheral
circuit 56 is connected to the VCC terminal. The CPU and peripheral
circuit 56 performs on-off control of the USB function circuit 55
based on the output of the counter 60.
[0056] The resistance R1 whose one terminal is connected to the
VREG terminal, and the other terminal is connected to a USB
communication line for transmission of the D- electrical potential
is provided. The resistance R1 pulls up the D- electrical potential
at the VREG electrical potential in the case of low rate USB
communication.
[0057] Although not shown here, the detector 51 is connected to a
personal computer through the plug 59, cable, and a plug in the
personal computer is the same manner as explained with reference to
the conventional detector.
[0058] Moreover, the D- electrical potential is pulled up to VREGX
(R2/(R1+R2)) V and the D+ electrical potential is pulled down by
the resistance R2, as there is no output by the resistance R1 and
the resistance R2 of the personal computer together with the MCU 53
and the root hub of the personal computer in the case of no
communication.
[0059] The detector 51 operates as follows. Potential VBUS is
supplied to the oscillation circuit 58 for oscillation in a state
where the cable is connected to the plug 59. Oscillation output
from the oscillation circuit 58 is input to the counter 60 which
outputs a detection signal to the CPU and peripheral circuit 56
after a predetermined number of counts. That is, the CPU and
peripheral circuit 56 may detect the connection state of the cable
by overflow of the counter 60. The CPU and peripheral circuit 56
outputs the Enable signal to the USB function circuit 55, and the
USB function circuit 55 outputs the output VREG of the built-in
regulator.
[0060] When the detector 51 and the personal computer are not
connected to each other, the oscillation circuit 58 does not
oscillate. Accordingly, whether the detector 51 and the personal
computer are connected to each other can be detected by
confirmation, with the CPU and peripheral circuit 56, of a counting
state where oscillation output from the oscillation circuit 58
under the connection state of the cable is counted by a counter
60.
[0061] According to the fourth embodiment, the similar advantages
to those of the first embodiment may be expected by provision of an
MCU comprising the oscillation circuit for transmission of an
input/output from/to the oscillator; and a counter for input from
the oscillation output from an oscillation circuit.
[0062] FIG. 5 is a block diagram of a detector 71 according to a
fifth embodiment of the present invention. The detector 71
comprises MCU 73, battery power supply 77 for supplying of
predetermined electrical potential to the MCU 73, plug 79
transmitting specific electrical potential to the MCU 73, plug 79
for transmission of specific electrical potential to the MCU 73,
and the oscillator 81.
[0063] The MCU 73 comprises the USB function circuit 75, CPU and
peripheral circuit 76, oscillation circuit 78, counter 80 for
counting of the oscillation output from the oscillation circuit 78,
and the PLL circuit 82 for generation of a clock for operations of
the USB function circuit 75 by frequency multiplication of the
oscillation output from the oscillation circuit 78. Furthermore,
the MCU 73 comprises a VCC terminal for input of a VCC level signal
from the battery power supply 77, D+ terminal which is connected to
the plug 79 for transmission of a D+ electric level, and a D-
terminal which is connected to the plug 79 for transmission of a D-
electric level. The MCU 73 also comprises a VREG terminal for
transmission of the output VREG of a regulator built in the USB
function circuit 75, and a VBUS terminal which is connected to the
plug 79 for transmission of VBUS (electrical potential supplied
from the personal computer). In addition, the MCU 73 comprises a
XIN terminal, and a XOUT terminal for transmission of an
input/output signal which is input to the oscillation circuit 78
from the oscillator 81 and vice versa.
[0064] The oscillation circuit 78 is connected to the VBUS
terminal, XIN terminal and the XOUT terminal. The oscillation
circuit 78 performs transmission of the oscillation output to the
counter 80 and the PLL circuit 82. The USB function circuit 75 is
connected to the D+ terminal, D- terminal, VREG terminal, and the
VBUS terminal. The PLL circuit 82 supplies a clock to the USB
function circuit 75.
[0065] The CPU and peripheral circuit 76 is connected to the VCC
terminal. The CPU and peripheral circuit 76 performs on-off control
of the USB function circuit 75 based on the output of the counter
80.
[0066] The resistance R1 whose one terminal is connected to the
VREG terminal and the other terminal is connected to a USB
communication line for transmission of the D- electrical potential
is provided. The resistance R1 pulls up the D- electrical potential
at the VREG electrical potential.
[0067] Although not shown here, the detector 71 is connected to a
personal computer through the plug 79, cable, and a plug in the
personal computer is the same manner as explained with reference to
the conventional detector.
[0068] Moreover, the D- electrical potential is pulled up to VREGX
(R2/(R1+R2)) V and the D+ electrical potential is pulled down by
the resistance R2, as there is no output by the resistance R1 and
the resistance R2 of the personal computer together with the MCU 73
and the root hub of the personal computer in the case of no
communication.
[0069] The detector 71 operates as follows. Potential VBUS is
supplied to the oscillation circuit 78 for oscillation in a state
where the cable is connected to the plug 79. Oscillation output
from the oscillation circuit 78 is input to the counter 80 which
outputs a detection signal to the CPU and peripheral circuit 76
after a predetermined number of counts. The PLL circuit 82 that
outputs a clock for operations to the USB function circuit 75 by
input and frequency multiplication of the oscillation output from
the oscillation circuit 78. The CPU and peripheral circuit 76
outputs the Enable signal to the USB function circuit 75, and the
USB function circuit 75 outputs the output VREG of the built-in
regulator.
[0070] When the detector 71 and the personal computer are not
connected to each other, the oscillation circuit 78 does not
oscillate. Accordingly, whether the detector 71 and the personal
computer are connected to each other can be detected by
confirmation, with the CPU and peripheral circuit 76, of a counting
state where oscillation output from the oscillation circuit 78
under the connection state of the cable is counted by a counter
80.
[0071] According to the fifth embodiment, more intelligent
connection detection, compared with that of the fourth embodiment,
maybe realized by provision of the MCU provided with the
oscillation circuit for transmission of the input/output form the
oscillator; the counter for input of the oscillation output from
the oscillation circuit; and the PLL circuit for generation of a
clock for operations of the USB function circuit by frequency
multiplication of the oscillation output from the oscillation
circuit.
[0072] Moreover, when a clock for operations of the USB function
circuit is commonly used as the oscillation output from the
oscillation circuit, a specially dedicated oscillation circuit may
be eliminated, as only a counter is required for a circuit
functioning only as detection unit.
[0073] In addition, there is also an advantage that the clock for
operations of the USB function circuit is commonly used as the
oscillation circuit for detection of whether the detector 71 and
the personal computer are connected to each other.
[0074] According to a sixth embodiment of the present invention,
the detector comprises a MCU that includes a comparator instead of
the A-D converter shown in FIG. 2. Other configuration is the same
as that shown in FIG. 2. However, the threshold for the comparator
is assumed to be controlled enough to detect the difference of the
D- electrical potential between a connection state and a
non-connection state of the cable.
[0075] Whether the detector according to the sixth embodiment and
the personal computer are connected to each other can be detected
by detection, with the inverter, of the difference in the D-
electrical potential between the connection state and the
non-connection state of the cable.
[0076] Thus, according to the sixth embodiment, more intelligent
connection detection, than that of the second embodiment, may be
realized by provision of the MCU comprising the comparator. The
comparator has a simpler configuration as compared to the A-D
converter, therefore, cost reduction becomes possible, and circuit
becomes simple.
[0077] According to a sixth embodiment of the present invention,
the detector comprises a MCU that includes an inverter instead of
the A-D converter shown in FIG. 2. Other configuration is the same
as that shown in FIG. 2. However, the threshold for the inverter is
assumed to be designed enough to detect the difference of the D-
electrical potential between a connection state and a
non-connection state of the cable.
[0078] Whether the detector according to the seventh embodiment and
the personal computer are connected to each other can be detected
by detection, with the inverter, of the difference in the D-
electrical potential between the connection state and the
non-connection state of the cable.
[0079] According to the seventh embodiment, more intelligent
connection detection, than that of the second embodiment, may be
realized by provision of the MCU comprising the inverter.
[0080] Moreover, the detection function may be realized by using an
inverter with appropriately adjusted threshold (enough to detect
the changes in the D- electrical potential), that is, by a simpler
configuration than that of a comparator according to the sixth
embodiment.
[0081] As explained above, according to the detector of one aspect
of this invention, intelligent and small-sized detector with low
power consumption is obtained. Furthermore, a dedicated circuit for
detection that is used conventionally is not required.
[0082] Also, the MCU is provided with the control function as a
peripheral device. The peripheral device is activated using
built-in battery and the operation of the USB function circuit is
stopped when the detector and the personal computer are not
connected, thereby achieving reduction in the power consumption.
Furthermore, when the detector and the personal computer are
connected, the operation of the USB function circuit is restarted,
and the battery is charged by the potential from the personal
computer.
[0083] Furthermore, a A-D converter is provided which may be
commonly used if the peripheral device requires A-D conversion. The
A-D converter may be replaced with a comparator. The comparator has
a simpler configuration as compared to the A-D converter.
Furthermore, the A-D converter may be replaced with an inverter.
The inverter has a simpler configuration as compared to the A-D
converter.
[0084] According to the method of another aspect of this invention,
fine detection of the connection with low power consumption may be
efficiently performed.
[0085] Although the invention has been described with respect to a
specific embodiment for a complete and clear disclosure, the
appended claims are not to be thus limited but are to be construed
as embodying all modifications and alternative constructions that
may occur to one skilled in the art which fairly fall within the
basic teaching herein set forth.
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