PIC16F87XA
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 9-31). 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 attempt-
ing to drive a data ’0’ (Figure 9-32).
9.4.17.3
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 sam-
pled low before SDA goes high.
FIGURE 9-31:
BUS COLLISION DURING A STOP CONDITION (CASE 1)
SDA sampled
TBRG
TBRG
TBRG
low after TBRG,
set BCLIF.
SDA
SDA asserted low
SCL
PEN
BCLIF
P
’0’
’0’
SSPIF
FIGURE 9-32:
BUS COLLISION DURING A STOP CONDITION (CASE 2)
TBRG
TBRG
TBRG
SDA
SCL goes low before SDA goes high,
set BCLIF.
Assert SDA
SCL
PEN
BCLIF
P
’0’
’0’
SSPIF
2001 Microchip Technology Inc.
Advance Information
DS39582A-page 107
MICROCHIP [ MICROCHIP ]
