PIC18C242 MICROCHIP [Microchip Technology], PIC18C242 Datasheet - Page 149

• Manufacturer Part Number: PIC18C242
• Description: High-Performance Microcontrollers with 10-Bit A/D
• Manufacturer: MICROCHIP [Microchip Technology]

14.3.16.3 BUS COLLISION DURING A STOP
Bus collision occurs during a STOP condition if:
a)
b)
FIGURE 14-29: BUS COLLISION DURING A STOP CONDITION (CASE 1)
FIGURE 14-30: BUS COLLISION DURING A STOP CONDITION (CASE 2)
7/99 Microchip Technology Inc.
After the SDA pin has been de-asserted and
allowed to float high, SDA is sampled low after
the BRG has timed out.
After the SCL pin is de-asserted, SCL is sam-
pled low before SDA goes high.
SDA
SCL
PEN
BCLIF
P
SSPIF
SSPIF
BCLIF
CONDITION
SDA
PEN
SCL
P
Assert SDA
T
SDA asserted low
BRG
T
BRG
Preliminary
T
BRG
T
BRG
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 14-29). 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 attempt-
ing to drive a data ’0’ (Figure 14-30).
SCL goes low before SDA goes high
Set BCLIF
T
BRG
T
BRG
PIC18CXX2
’0’
’0’
DS39026B-page 149
SDA sampled
low after T
Set BCLIF
’0’
’0’
BRG
,