Datasheet

PIC16C77X
DS30275B-page 94 Advance Information  1999-2013 Microchip Technology Inc.
8.2.18.17 BUS COLLISION DURING A STOP
CONDITION
Bus collision occurs during a STOP condition if:
a) After the SDA pin has been de-asserted and
allowed to float high, SDA is sampled low after
the BRG has timed out.
b) After the SCL pin is de-asserted, SCL is sam-
pled low before SDA goes high.
The STOP condition begins with SDA asserted low.
When SDA is sampled low, the SCL pin is allow to float.
When the pin is sampled high (clock arbitration), the
baud rate generator is loaded with SSPADD<6:0> and
counts down to 0. After the BRG times out SDA is sam-
pled. If SDA is sampled low, a bus collision has
occurred. This is due to another master attempting to
drive a data '0'. If the SCL pin is sampled low before
SDA is allowed to float high, a bus collision occurs.
This is another case of another master attempting to
drive a data '0' (Figure 8-40).
FIGURE 8-40: BUS COLLISION DURING A STOP CONDITION (CASE 1)
FIGURE 8-41: BUS COLLISION DURING A STOP CONDITION (CASE 2)
SDA
SCL
BCLIF
PEN
P
SSPIF
TBRG TBRG TBRG
SDA asserted low
SDA sampled
low after T
BRG,
Set BCLIF
'0'
'0'
'0'
'0'
SDA
SCL
BCLIF
PEN
P
SSPIF
TBRG TBRG TBRG
Assert SDA
SCL goes low before SDA goes high
Set BCLIF
'0'
'0'
774.book Page 94 Tuesday, January 29, 2013 12:02 PM