PIC18F97J60_11 Datasheet, PDF (312/492 Pages) Microchip Technology – 64/80/100-Pin, High-Performance, 1-Mbit Flash Microcontrollers with Ethernet

PIC18F97J60 FAMILY
20.4.17.3 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 20-33). 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 20-34).
FIGURE 20-33:
BUS COLLISION DURING A STOP CONDITION (CASE 1)
TBRG
TBRG
TBRG
SDAx
SCLx
SDAx asserted low
PEN
BCLxIF
P
SSPxIF
SDAx sampled
low after TBRG,
set BCLxIF
‘0’
‘0’
FIGURE 20-34: BUS COLLISION DURING A STOP CONDITION (CASE 2)
TBRG
TBRG
TBRG
SDAx
SCLx
Assert SDAx
SCLx goes low before SDAx goes high,
set BCLxIF
PEN
BCLxIF
P
‘0’
SSPxIF
‘0’
DS39762F-page 312
 2011 Microchip Technology Inc.