PIC18F23K20_10 Datasheet, PDF (208/456 Pages) Microchip Technology – 28/40/44-Pin Flash Microcontrollers with nanoWatt XLP Technology

PIC18F2XK20/4XK20
17.4.3.2 Reception
When the R/W bit of the address byte is clear and an
address match occurs, the R/W bit of the SSPSTAT
register is cleared. The received address is loaded into
the SSPBUF register and the SDA 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 bit of the SSPSTAT
register is set, or bit SSPOV bit of the SSPCON1
register is set.
An MSSP interrupt is generated for each data transfer
byte. Flag bit, SSPIF of the PIR1 register, must be
cleared by software. The SSPSTAT register is used to
determine the status of the byte.
When the SEN bit of the SSPCON2 register is set,
SCK/SCL will be held low (clock stretch) following
each data transfer. The clock must be released by
setting the CKP bit of the SSPCON1 register. See
Section 17.4.4 “Clock Stretching” for more detail.
17.4.3.3 Transmission
When the R/W bit of the incoming address byte is set
and an address match occurs, the R/W bit of the
SSPSTAT register is set. The received address is
loaded into the SSPBUF register. The ACK pulse will
be sent on the ninth bit and pin SCK/SCL is held low
regardless of SEN (see Section 17.4.4 “Clock
Stretching” for more detail). 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 SSPBUF register
which also loads the SSPSR register. Then pin
SCK/SCL should be enabled by setting the CKP bit of
the SSPCON1 register. The eight data bits are shifted
out on the falling edge of the SCL input. This ensures
that the SDA signal is valid during the SCL high time
(Figure 17-9).
The ACK pulse from the master-receiver is latched on
the rising edge of the ninth SCL input pulse. If the SDA
line is high (not ACK), then the data transfer is
complete. In this case, when the ACK is latched by the
slave, the slave logic is reset (resets SSPSTAT
register) and the slave monitors for another occurrence
of the Start bit. If the SDA line was low (ACK), the next
transmit data must be loaded into the SSPBUF register.
Again, pin SCK/SCL must be enabled by setting bit
CKP.
An MSSP interrupt is generated for each data transfer
byte. The SSPIF bit must be cleared by software and
the SSPSTAT register is used to determine the status
of the byte. The SSPIF bit is set on the falling edge of
the ninth clock pulse.
DS41303G-page 208
 2010 Microchip Technology Inc.