PIC18F45J10 FAMILY
16.4.3.3
Reception
16.4.3.4
Transmission
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 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 RC3 or RD6 is held low,
regardless of SEN (see Section 16.4.4 “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 regis-
ter which also loads the SSPxSR register. Then pin
RC3 or RD0 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 16-9).
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), SCKx/SCLx
(RC3 or RD0) will be held low (clock stretch) following
each data transfer. The clock must be released by
setting bit, CKP (SSPxCON1<4>). See Section 16.4.4
“Clock Stretching” for more details.
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 logic is reset (resets SSPxSTAT
register) and 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 regis-
ter. Again, pin RC3 or RD0 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.
DS39682E-page 166
© 2009 Microchip Technology Inc.
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