PIC18F-LF1XK50 Datasheet, PDF (169/420 Pages) Microchip Technology – 20-Pin USB Flash Microcontrollers

15.3.8
I²C MASTER MODE START
CONDITION TIMING
To initiate a Start condition, the user sets the Start
Enable bit, SEN bit of the SSPCON2 register. If the
SDA and SCL pins are sampled high, the Baud Rate
Generator is reloaded with the contents of
SSPADD<6:0> and starts its count. If SCL and SDA are
both sampled high when the Baud Rate Generator
times out (TBRG), the SDA pin is driven low. The action
of the SDA being driven low while SCL is high is the
Start condition and causes the S bit of the SSPSTAT1
register to be set. Following this, the Baud Rate Gener-
ator is reloaded with the contents of SSPADD<7:0>
and resumes its count. When the Baud Rate Generator
times out (TBRG), the SEN bit of the SSPCON2 register
will be automatically cleared by hardware; the Baud
Rate Generator is suspended, leaving the SDA line
held low and the Start condition is complete.
PIC18F/LF1XK50
Note:
If at the beginning of the Start condition,
the SDA and SCL pins are already sam-
pled low, or if during the Start condition,
the SCL line is sampled low before the
SDA line is driven low, a bus collision
occurs, the Bus Collision Interrupt Flag,
BCLIF, is set, the Start condition is aborted
and the I²C module is reset into its Idle
state.
15.3.8.1 WCOL Status Flag
If the user writes the SSPBUF when a Start sequence
is in progress, the WCOL 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
SSPCON2 is disabled until the Start
condition is complete.
FIGURE 15-19: FIRST START BIT TIMING
Write to SEN bit occurs here
SDA = 1,
SCL = 1
Set S bit (SSPSTAT<3>)
At completion of Start bit,
hardware clears SEN bit
and sets SSPIF bit
TBRG
TBRG
Write to SSPBUF occurs here
SDA
1st bit
TBRG
2nd bit
SCL
TBRG
S
 2010 Microchip Technology Inc.
Preliminary
DS41350E-page 169