Datasheet

PIC17C7XX
DS30289C-page 174  1998-2013 Microchip Technology Inc.
15.2.18.3 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 allowed 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 sampled. 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 15-40).
FIGURE 15-40: BUS COLLISION DURING A STOP CONDITION (CASE 1)
FIGURE 15-41: 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'