PIC18F2420-I/SOC01 Microchip, PIC18F2420-I/SOC01 Datasheet - Page 191

• Manufacturer Part Number: PIC18F2420-I/SOC01
• Description: 28 pin, 16 kb flash, 3804 ram, 25 i/o...
• Manufacturer: Microchip

17.4.8
To initiate a Start condition, the user sets the Start
Enable bit, SEN (SSPCON2<0>). 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 (T
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. Following 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
(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 17-19:
© 2008 Microchip Technology Inc.
I
CONDITION TIMING
2
C MASTER MODE START
Write to SEN bit occurs here
FIRST START BIT TIMING
SDA
SCL
BRG
), the SEN bit
BRG
), the SDA
PIC18F2420/2520/4420/4520
SDA = 1,
SCL = 1
T
BRG
Set S bit (SSPSTAT<3>)
T
S
BRG
At completion of Start bit,
hardware clears SEN bit
17.4.8.1
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).
and sets SSPIF bit
Note:
Note:
T
Write to SSPBUF occurs here
BRG
1st bit
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
Because queueing of events is not
allowed, writing to the lower 5 bits of
SSPCON2 is disabled until the Start
condition is complete.
2
C module is reset into its Idle state.
WCOL Status Flag
T
BRG
2nd bit
DS39631E-page 189