PIC16C770 Microchip Technology Inc., PIC16C770 Datasheet - Page 100

• Manufacturer Part Number: PIC16C770
• Description: 18/20-pin, 8-bit Cmos Microcontrollers With 10/12-bit A/d
• Manufacturer: Microchip Technology Inc.

PIC16C717/770/771
9.2.17.3
Bus collision occurs during a STOP condition if:
a)
b)
FIGURE 9-29:
FIGURE 9-30:
DS41120B-page 98
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
BUS COLLISION DURING A STOP
CONDITION
SDA
PEN
SCL
P
’0’
’0’
’0’
’0’
BUS COLLISION DURING A STOP CONDITION (CASE 1)
BUS COLLISION DURING A STOP CONDITION (CASE 2)
Assert SDA
SDA asserted low
T
BRG
T
BRG
Advance Information
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 9-29). 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 9-30).
SCL goes low before SDA goes high
Set BCLIF
T
BRG
T
BRG
2002 Microchip Technology Inc.
’0’
’0’
SDA sampled
low after T
Set BCLIF
BRG
,