PIC18F4539 Datasheet, PDF (165/322 Pages) Microchip Technology – Enhanced FLASH Microcontrollers with Single Phase Induction Motor Control Kernel

PIC18FXX39
16.4.17.3 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
sampled 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' (Figure 16-31). 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 16-32).
FIGURE 16-31:
BUS COLLISION DURING A STOP CONDITION (CASE 1)
TBRG
TBRG
TBRG
SDA
SCL
SDA asserted low
PEN
SDA sampled
low after TBRG,
Set BCLIF
BCLIF
P
'0'
SSPIF
'0'
FIGURE 16-32:
SDA
SCL
PEN
BCLIF
P
SSPIF
BUS COLLISION DURING A STOP CONDITION (CASE 2)
TBRG
TBRG
TBRG
Assert SDA
SCL goes low before SDA goes high,
Set BCLIF
'0'
'0'
 2002 Microchip Technology Inc.
Preliminary
DS30485A-page 163