PIC18F87K22 Datasheet, PDF (323/548 Pages) Microchip Technology – 64/80-Pin, High-Performance, 1-Mbit Enhanced Flash Microcontrollers with 12-Bit A/D and nanoWatt XLP Technology

PIC18F87K22 FAMILY
21.4.17.3 Bus Collision During a Stop
Condition
Bus collision occurs during a Stop condition if:
a) After the SDAx pin has been deasserted and
allowed to float high, SDAx is sampled low after
the BRG has timed out.
b) After the SCLx pin is deasserted, SCLx is
sampled low before SDAx goes high.
The Stop condition begins with SDAx asserted low.
When SDAx is sampled low, the SCLx pin is allowed to
float. When the pin is sampled high (clock arbitration),
the Baud Rate Generator is loaded with
SSPxADD<6:0> and counts down to 0. After the BRG
times out, SDAx is sampled. If SDAx is sampled low, a
bus collision has occurred. This is due to another
master attempting to drive a data ‘0’ (Figure 21-33). If
the SCLx pin is sampled low before SDAx is allowed to
float high, a bus collision occurs. This is another case
of another master attempting to drive a data ‘0’
(Figure 21-34).
FIGURE 21-33:
SDAx
SCLx
PEN
BUS COLLISION DURING A STOP CONDITION (CASE 1)
TBRG
TBRG
TBRG
SDAx Asserted Low
SDAx Sampled
Low After TBRG,
Set BCLxIF
BCLxIF
P
‘0’
SSPxIF
‘0’
FIGURE 21-34:
SDAx
SCLx
PEN
BCLxIF
P
SSPxIF
BUS COLLISION DURING A STOP CONDITION (CASE 2)
TBRG
TBRG
TBRG
Assert SDAx
SCLx goes Low Before SDAx goes High,
Set BCLxIF
‘0’
‘0’
 2010 Microchip Technology Inc.
Preliminary
DS39960B-page 323