Datasheet

 2010 Microchip Technology Inc. Preliminary DS39974A-page 343
PIC18F47J13 FAMILY
20.5.17.3 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 BRG 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)
FIGURE 20-34: BUS COLLISION DURING A STOP CONDITION (CASE 2)
SDAx
SCLx
BCLxIF
PEN
P
SSPxIF
TBRG TBRG TBRG
SDAx Asserted Low
SDAx Sampled
Low after T
BRG,
Set BCLxIF
‘0’
‘0’
SDAx
SCLx
BCLxIF
PEN
P
SSPxIF
TBRG TBRG TBRG
Assert SDAx
SCLx goes Low Before SDAx goes High,
Set BCLxIF
‘0’
‘0’