PIC18F44J50-I Datasheet, PDF (296/562 Pages) Microchip Technology – 28/44-Pin, Low-Power, High-Performance USB Microcontrollers

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19.5.3.5 Reception
When the R/W bit of the address byte is clear and an
address match occurs, the R/W bit of the SSPxSTAT
register is cleared. The received address is loaded into
the SSPxBUF register and the SDAx line is held low
(ACK).
When the address byte overflow condition exists, then
the no Acknowledge (ACK) pulse is given. An overflow
condition is defined as either bit, BF (SSPxSTAT<0>),
is set or bit, SSPOV (SSPxCON1<6>), is set.
An MSSP interrupt is generated for each data transfer
byte. The interrupt flag bit, SSPxIF, must be cleared in
software. The SSPxSTAT register is used to determine
the status of the byte.
If SEN is enabled (SSPxCON2<0> = 1), SCLx will be
held low (clock stretch) following each data transfer.
The clock must be released by setting bit, CKP
(SSPxCON1<4>). See Section 19.5.4 “Clock
Stretching” for more details.
19.5.3.6 Transmission
When the R/W bit of the incoming address byte is set
and an address match occurs, the R/W bit of the
SSPxSTAT register is set. The received address is
loaded into the SSPxBUF register. The ACK pulse will
be sent on the ninth bit and pin SCLx is held low regard-
less of SEN (see Section 19.5.4 “Clock Stretching”
for more details). By stretching the clock, the master
will be unable to assert another clock pulse until the
slave is done preparing the transmit data. The transmit
data must be loaded into the SSPxBUF register, which
also loads the SSPxSR register. Then, the SCLx pin
should be enabled by setting bit, CKP
(SSPxCON1<4>). The eight data bits are shifted out on
the falling edge of the SCLx input. This ensures that the
SDAx signal is valid during the SCLx high time
(Figure 19-10).
The ACK pulse from the master-receiver is latched on
the rising edge of the ninth SCLx input pulse. If the SDAx
line is high (not ACK), then the data transfer is complete.
In this case, when the ACK is latched by the slave, the
slave monitors for another occurrence of the Start bit. If
the SDAx line was low (ACK), the next transmit data
must be loaded into the SSPxBUF register. Again, the
SCLx pin must be enabled by setting bit, CKP.
An MSSP interrupt is generated for each data transfer
byte. The SSPxIF bit must be cleared in software and
the SSPxSTAT register is used to determine the status
of the byte. The SSPxIF bit is set on the falling edge of
the ninth clock pulse.
DS39931D-page 296
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