SAM4L Datasheet, PDF (715/1185 Pages) ATMEL Corporation – ATSAM ARM-based Flash MCU

ATSAM4L4/L2
In combined transfers, the PECEN bit should only be written to one in the last of the combined
transfers. Consider the following transfer:
S, ADR+W, COMMAND_BYTE, ACK, SR, ADR+R, DATA_BYTE, ACK, PEC_BYTE, NACK, P
This transfer is generated by writing two commands to the command registers. The first com-
mand is a write with NBYTES=1 and PECEN=0, and the second is a read with NBYTES=2 and
PECEN=1.
Writing a one to the STOP bit in CR will place a STOP condition on the bus after the current
byte. No PEC byte will be sent in this case.
27.8.9.2
Timeouts
The TLOWS and TLOWM fields in SMBTR configure the SMBus timeout values. If a timeout
occurs, the master will transmit a STOP condition and leave the bus. The SR.TOUT bit is set.
27.8.10
Identifying Bus Events
This chapter lists the different bus events, and how they affect bits in the TWIM registers. This is
intended to help writing drivers for the TWIM.
Table 27-5. Bus Events
Event
Master transmitter has sent
a data byte
Master receiver has
received a data byte
Start+Sadr sent, no ack
received from slave
Data byte sent to slave, no
ack received from slave
Arbitration lost
SMBus timeout received
Effect
SR.THR is cleared.
SR.RHR is set.
SR.ANAK is set.
SR.CCOMP not set.
CMDR.VALID remains set.
STOP automatically transmitted on bus.
SR.DNAK is set.
SR.CCOMP not set.
CMDR.VALID remains set.
STOP automatically transmitted on bus.
SR.ARBLST is set.
SR.CCOMP not set.
CMDR.VALID remains set.
TWCK and TWD immediately released to a pulled-up state.
SR.SMBTOUT is set.
SR.CCOMP not set.
CMDR.VALID remains set.
STOP automatically transmitted on bus.
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