PIC18F67J11-IPT Datasheet, PDF (257/448 Pages) Microchip Technology – 64/80-Pin High-Performance, 1-Mbit Flash Microcontrollers with nanoWatt Technology

PIC18F87J11 FAMILY
19.4.8
I²C MASTER MODE START
CONDITION TIMING
To initiate a Start condition, the user sets the Start
Enable bit, SEN (SSPxCON2<0>). If the SDAx and
SCLx pins are sampled high, the Baud Rate Generator
is reloaded with the contents of SSPxADD<6:0> and
starts its count. If SCLx and SDAx are both sampled
high when the Baud Rate Generator times out (TBRG),
the SDAx pin is driven low. The action of the SDAx
being driven low while SCLx is high is the Start condi-
tion and causes the S bit (SSPxSTAT<3>) to be set.
Following this, the Baud Rate Generator is reloaded
with the contents of SSPxADD<6:0> and resumes its
count. When the Baud Rate Generator times out
(TBRG), the SEN bit (SSPxCON2<0>) will be
automatically cleared by hardware. The Baud Rate
Generator is suspended, leaving the SDAx line held low
and the Start condition is complete.
Note:
If, at the beginning of the Start condition,
the SDAx and SCLx pins are already sam-
pled low or if during the Start condition, the
SCLx line is sampled low before the SDAx
line is driven low, a bus collision occurs,
the Bus Collision Interrupt Flag, BCLxIF, is
set, the Start condition is aborted and the
I²C module is reset into its Idle state.
19.4.8.1 WCOL Status Flag
If the user writes the SSPxBUF when a Start sequence
is in progress, the WCOL bit is set and the contents of
the buffer are unchanged (the write doesn’t occur).
Note:
Because queueing of events is not
allowed, writing to the lower 5 bits of
SSPxCON2 is disabled until the Start
condition is complete.
FIGURE 19-21: FIRST START BIT TIMING
Write to SEN bit occurs here
SDAx = 1,
SCLx = 1
Set S bit (SSPxSTAT<3>)
At completion of Start bit,
hardware clears SEN bit
and sets SSPxIF bit
TBRG
TBRG
Write to SSPxBUF occurs here
SDAx
1st bit
TBRG
2nd bit
SCLx
TBRG
S
© 2009 Microchip Technology Inc.
DS39778D-page 257