# US 5,710,890 A · Method and device for the transmission of data on a bus

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- Number: US 5,710,890 A
- Document ID: US5710890A
- Status: Granted
- Kind: A
- Application number: 08/573,853
- Filed: 1995-12-18
- Granted: 1998-01-20
- Earliest claimed: 1994-12-21
- Assignees: U.S. Philips Corporation
- Inventors: Jean-Pierre Hermer
- Web page: https://patentgrep.com/patent/US5710890A

## CPC

- G06F 13/423: {with synchronous protocol}
- G06F 13/4213: {with asynchronous protocol}
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)

## Abstract

With a two-wire bus, the method is to be used in a system which comprises only a master and a slave. Before generating a "start" signal of the customary type, the master requesting the dialog pulls the clock wire to zero for a period which is limited but long enough (2-3), for example more than 1 mS, and also pulls the data wire to zero. The slave responds by pulling the clock wire to zero (5) for a period of time of the same order of magnitude, after which the master resets the data wire (6) and initiates a customary start procedure (7). In the case where the slave requests the dialog, only the clock wire is pulled to zero during the first phase.

## Claims

### Claim 1

A method for the transmission of data with the help of a two-wire bus, carried out in a device comprising:
a master station which enables control of the transmission and reception of data and comprises a data terminal and a clock terminal,
a slave station which enables the transmission and reception of data and comprises a data terminal and a clock terminal,
a data wire which interconnects the data terminals of the stations,
a clock wire which interconnects the clock terminals of the stations,
means for maintaining the bus wires at a first voltage level in the absence of forcing by the stations,
each of the stations being capable of forcing one of the bus wires to a second voltage level, and the master station being capable of producing a start signal, which indicates that it is ready to control the transmission of data, characterized in that before the production of a start signal the master station
forces its clock terminal and subsequently its data terminal to the second voltage level,
subsequently maintains its clock terminal at the second voltage level for a predetermined first period of time after which it allows it to return to the first level
the slave station
tests whether its clock terminal and its data terminal are at the second voltage level, and in that case
detects subsequently whether its clock terminal returns to the fast voltage level,
and then forces its clock terminal to the second voltage level for a predetermined second period of time, after which it allows it to return to the first level,
and during this period the master station
tests whether its clock terminal is maintained at the second voltage level during said second predetermined period of time and if it subsequently returns to the first level,
and then allows its data terminal to return to the first level, and said start signal is then generated.

### Claim 2 (depends on 1)

A method for the transmission of data as claimed in claim 1, characterized in that before the formation of a start signal:
the slave station
forces its clock terminal to the second voltage level,
subsequently maintains its clock terminal at the second voltage level during a third predetermined period of time, after which it allows it to return to the first level,
the master station
tests if its clock terminal is at the second voltage level and in that case
subsequently checks if its clock terminal returns to the first voltage level,
and then forces its clock terminal to the second voltage level during a predetermined fourth period of time, after which it allows it to return to the first level, and said start signal is then generated,
and during this time the slave station
checks if its clock terminal is maintained at the second voltage level during said fourth predetermined period and if it subsequently returns to the first level,
and then awaits the start signal generated by the master to transmit data in synchronism with the clock generated by the master.

### Claim 3

A device for the transmission of data with the help of a bus, comprising:
a master station which comprises a microprocessor which enables control of the transmission and reception of data and comprises a data terminal and a clock terminal,
a slave station which comprises a microprocessor which enables the transmission and reception of data and comprises a data terminal and a clock terminal,
a data wire which interconnects the data terminals of the stations,
a clock wire which interconnects the clock terminals of the stations,
means for maintaining the bus wires at a first voltage level in the absence of forcing by the stations,
means in each station for forcing one of the bus wires to a second voltage level, and
means in the master station for producing a start signal which indicates that it is ready to control the transmission data,
characterized in that
in order to generate a dialog request signal, the microprocessor of the master station comprises software means
for forcing its clock terminal and subsequently its data terminal to the second voltage level,
for subsequently maintaining its clock terminal at the second voltage level during a predetermined first period of time, and subsequently allowing it to return to the first level,
in order to respond to a dialog request signal from the master, the microprocessor of the slave station comprises software means
for testing whether if its clock terminal and its data terminal are at the second voltage level,
for detecting that its clock terminal is returned to the first voltage level after having detected that it was at the second voltage level,
and for then forcing its clock terminal to the second voltage level during a second predetermined period of time, and subsequently allowing it to return to the first level,
the microprocessor of the master station comprises also software means
for detecting, after having generated the dialog request signal, that its clock terminal is maintained at the second voltage level during said second predetermined period of time and that it subsequently returns to the first level,
and for then allowing its data terminal to return to the first level, after which said start signal is generated.

### Claim 4 (depends on 3)

A device for the transmission of data as claimed in claim 3, characterized in that
in order to generate a dialog request signal from the slave, the microprocessor of the slave station comprises software means
for forcing its clock terminal to the second voltage level,
for subsequently maintaining its flock terminal at the second voltage level during a predetermined first period of time, and for subsequently allowing it to return to the first level,
in order to respond to a dialog request signal from the slave, the microprocessor of the master station comprises software means
for testing if its clock terminal is at the second voltage level,
for detecting that its clock terminal is returned to the first voltage level after having detected that it was at the second voltage level,
and for then forcing its clock terminal to the second voltage level during a second predetermined period of time, and for subsequently allowing it to return to the first level,
said start signal then being generated,
the microprocessor of the slave station comprising software means
for detecting, after having generated a dialog request signal, that its clock terminal is maintained at the second voltage level during said second predetermined period of time and that it subsequently returns to the first level,
for then detecting the start signal generated by the master and for subsequently transmitting data in synchronism with the clock generated by the master.

### Claim 5 (depends on 3)

A car radio receiver, characterized in that it is equipped with a device as claimed in claim 3.

### Claim 6 (depends on 4)

A car radio receiver, characterized in that it is equipped with a device as claimed in claim 4.