UPSD3422 datasheet(132/293 Pages) STMICROELECTRONICS

132 / 293 page

I2C interface

uPSD34xx

132/293

Is this the next to last byte to receive from Slave?

If this is the next to last byte, do not allow Master to ACK

on next interrupt.

–

S1CON.AA = 0, don’t let Master return ACK

–

Exit ISR, now ready to recv last byte from Slv

If this is not next to last byte, let Master send ACK to

Slave

<S1CON.AA is already 1>

–

Exit ISR, ready to recv more bytes from Slave

Else If mode is Slave-Transmitter:

Is this Intr from SIOE detecting a STOP on bus?

If Yes, a STOP was detected:

–

S1DAT = dummy, write to release bus

–

Exit ISR, Master needs no more data bytes

If No, a STOP was not detected, continue:

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

If No, an ACK was not received:

–

S1DAT = dummy, write to release bus

–

Exit ISR, Master needs no more data bytes

If Yes, ACK was received, then continue:

–

S1DAT = xmit_buf[buffer_index], transmit byte

–

Exit ISR, transmit next byte on next interrupt

Else If mode is Slave-Receiver:

Is this Intr from SIOE detecting a STOP on bus?

If Yes, a STOP was detected:

–

recv_buf[buffer_index] = S1DAT, get last byte

–

Exit ISR, Master has sent last byte

If No, a STOP was not detected, continue:

Determine if this Interrupt is from receiving an address or a data

byte from a Master.

Is (S1CON.ADDR = 1 and S1CON.AA =1)?

If No, intr is from receiving data, goto C:

If Yes, intr is from an address, continue:

–

slave_is_adressed = 1, local variable set true

–

S1CON.ADDR = 0, clear address match flag

Determine if R/W bit indicates transmit or receive.

UPSD3422 Datasheet(PDF) 132 Page - STMicroelectronics

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