PIC18F25K80 MICROCHIP [Microchip Technology], PIC18F25K80 Datasheet - Page 335

• Manufacturer Part Number: PIC18F25K80
• Manufacturer: MICROCHIP [Microchip Technology]

21.4.17.2
During a Repeated Start condition, a bus collision
occurs if:
a)
b)
When the user deasserts SDA and the pin is allowed to
float high, the BRG is loaded with SSPADD<6:0> and
counts down to 0. The SCL pin is then deasserted and
when sampled high, the SDA pin is sampled.
FIGURE 21-31:
FIGURE 21-32:
 2011 Microchip Technology Inc.
A low level is sampled on SDA when SCL goes
from a low level to a high level.
SCL goes low before SDA is asserted low,
indicating that another master is attempting to
transmit a data ‘ 1 ’.
SDA
SCL
BCLIF
RSEN
S
SSPIF
SDA
SCL
RSEN
BCLIF
S
SSPIF
Bus Collision During a Repeated
Start Condition
BUS COLLISION DURING A REPEATED START CONDITION (CASE 1)
BUS COLLISION DURING REPEATED START CONDITION (CASE 2)
SCL goes low before SDA,
set BCLIF. Release SDA and SCL.
Preliminary
T
BRG
Sample SDA when SCL goes high.
If SDA = 0, set BCLIF and release SDA and SCL.
PIC18F66K80 FAMILY
If SDA is low, a bus collision has occurred (i.e., another
master
Figure
reloaded and begins counting. If SDA goes from
high-to-low before the BRG times out, no bus collision
occurs because no two masters can assert SDA at
exactly the same time.
If SCL goes from high-to-low before the BRG times out
and SDA has not already been asserted, a bus collision
occurs. In this case, another master is attempting to
transmit a data ‘ 1 ’ during the Repeated Start condition
(see
If, at the end of the BRG time-out, both SCL and SDA
are still high, the SDA pin is driven low and the BRG is
reloaded and begins counting. At the end of the count,
regardless of the status of the SCL pin, the SCL pin is
driven low and the Repeated Start condition is complete.
Figure
21-31). If SDA is sampled high, the BRG is
is
21-32).
attempting
Cleared in software
T
BRG
to
Interrupt cleared
in software
transmit
‘0’
‘0’
DS39977C-page 335
‘0’
a
data
‘ 0 ’,