PIC18C242 MICROCHIP [Microchip Technology], PIC18C242 Datasheet - Page 137

• Manufacturer Part Number: PIC18C242
• Description: High-Performance Microcontrollers with 10-Bit A/D
• Manufacturer: MICROCHIP [Microchip Technology]

14.3.6
To initiate a START condition, the user sets the start
condition enable bit SEN (SSPCON2<0>). If the SDA
and SCL pins are sampled high, the baud rate genera-
tor is re-loaded 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 (T
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 (SSPSTAT<3>) to be set. Follow-
ing this, the baud rate generator is reloaded with the
contents of SSPADD<6:0> and resumes its count.
When the baud rate generator times out (T
SEN bit (SSPCON2<0>) will be automatically cleared
by hardware, the baud rate generator is suspended
leaving the SDA line held low and the START condition
is complete.
FIGURE 14-16: FIRST START BIT TIMING
Note:
7/99 Microchip Technology Inc.
I
TIMING
2
C MASTER MODE START CONDITION
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
I
2
C module is reset into its IDLE state.
Write to SEN bit occurs here.
SDA
SCL
BRG
BRG
SDA = 1,
SCL = 1
T
), the
), the
BRG
Preliminary
Set S bit (SSPSTAT<3>)
T
S
BRG
At completion of start bit,
Hardware clears SEN bit
14.3.6.1
If the user writes the SSPBUF when an START
sequence is in progress, the WCOL is set and the con-
tents of the buffer are unchanged (the write doesn’t
occur).
and sets SSPIF bit
Note:
T
Write to SSPBUF occurs here
BRG
1st Bit
WCOL STATUS FLAG
Because queueing of events is not
allowed, writing to the lower 5 bits of
SSPCON2 is disabled until the START
condition is complete.
T
BRG
PIC18CXX2
2nd Bit
DS39026B-page 137