UPSD325X datasheet(81/176 Pages) STMICROELECTRONICS

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µPSD325X DEVICES

Programmer’s Guide for I2C and DDC2

The I2C serial I/O and DDC Interface operates in

four modes.

Master transmitter

Master receiver

Slave transmitter

Slave receiver

Master transmitter mode flow.

1. Read SxSTA.

2. If BBUSY == 1 then

go to step1.

Else then

write slave address to SxDAT and set both

ENI and STA, reset AA in SxCON.

3. Wait for interrupt.

4. Read SxSTA.

If BLOST == 1 or /ACK_REP == 1* then

write dummy data to SxDAT.

Go to step1.

Else then

clear STA.

5. Perform required service routines.

If this datum == LAST then

set STO in SxCON and write last data to Sx-

DAT**.

Go to step 6.

Else then

write next data to SxDAT**.

Go to step3.

6. Wait for interrupt.

Write dummy data to SxDAT**.

Note: 1. (*) If the master don’t receive the acknowledge from the

slave, it generates the STOP condition and returns to the

IDLE state.

2. (**) This action should be the last in service routine.

Slave transmitter mode flow.

1. Write slave address to SxADR, set AA and ENI

in SxCON.

2. Wait for interrupt.

3. Read SxSTA and write the first data to SxDAT*.

Reset AA in SxCON.

4. Wait for interrupt.

5. Read SxSTA.

If /ACK_REP == 1** then

Go to step7.

Else then

write the next SxDAT*.

Go to step5.

6. Write dummy data to SxDAT*.

Note: 1. (*) These actions should be the last.

2. (**) If the master want to stop the current data requests, it

don’t have to acknowledge to the slave transmitter.

3. If the slave does not receive the acknowledge from the

master, it releases the SDA and enters the IDLE state, so

if the master is to resume the data requests, it must re-

generate the START condition.

UPSD325X Datasheet(PDF) 81 Page - STMicroelectronics

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