UPSD3422 datasheet(131/293 Pages) STMICROELECTRONICS

131 / 293 page

uPSD34xx

I2C interface

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Else If mode is Master-Receiver:

Bus Arbitration lost? (status.BLOST=1?)

If Yes, Arbitration was lost:

–

S1DAT = dummy, write to release bus

–

Exit ISR, SIOE will switch to Slave Recv mode

If No, Aribitration was not lost, continue:

Is this Interrupt from sending an address to Slave, or is it from

receiving a data byte from Slave?

If its from sending Slave address, goto A:

If its from receiving Slave data, goto B:

(Interrupt is from Master sending addr to Slave)

ACK recvd from Slave? (status.ACK_RESP=0?)

If No, an ACK was not received:

–

S1CON.STO = 1, set STOP condition

–

dummy = S1DAT, read to release bus

–

Exit ISR

If Yes, ACK was received, then continue:

–

dummy = S1DAT, read to release bus

Does Master want to receive just one data byte?

If Yes, do not allow Master to ACK on next interrupt:

<S1CON.AA is already 0>

–

Exit ISR, now ready to recv one byte from Slv

If No, Master can ACK next byte from Slv

–

S1CON.AA = 1, allow Master to send ACK

–

Exit ISR, now ready to recv data from Slave

(Interrupt is from Master recving data from Slv)

–

recv_buf[buffer_index] = S1DAT, read byte

Is this the last data byte to receive from Slave?

If Yes, tell Slave to stop transmitting:

–

S1CON.STO = 1, set STOP bus condition

–

Exit ISR, finished receiving data from Slave

If No, continue:

UPSD3422 Datasheet(PDF) 131 Page - STMicroelectronics

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