PIC18F25J50 MICROCHIP [Microchip Technology], PIC18F25J50 Datasheet - Page 320

• Manufacturer Part Number: PIC18F25J50
• Description: 28/44-Pin, Low-Power, High-Performance USB Microcontrollers with nanoWatt XLP Technology
• Manufacturer: MICROCHIP [Microchip Technology]

PIC18F46J50 FAMILY
19.5.17.2
During a Repeated Start condition, a bus collision
occurs if:
a)
b)
When the user deasserts SDAx and the pin is allowed
to float high, the BRG is loaded with SSPxADD<6:0>
and counts down to 0. The SCLx pin is then deasserted
and when sampled high, the SDAx pin is sampled.
FIGURE 19-31:
FIGURE 19-32:
DS39931D-page 320
A low level is sampled on SDAx when SCLx
goes from a low level to a high level.
SCLx goes low before SDAx is asserted low,
indicating that another master is attempting to
transmit a data ‘1’.
SDAx
SCLx
BCLxIF
RSEN
S
SSPxIF
SDAx
SCLx
RSEN
BCLxIF
S
SSPxIF
Bus Collision During a Repeated
Start Condition
BUS COLLISION DURING A REPEATED START CONDITION (CASE 1)
BUS COLLISION DURING REPEATED START CONDITION (CASE 2)
SCLx goes low before SDAx,
set BCLxIF. Release SDAx and SCLx.
T
BRG
Sample SDAx when SCLx goes high.
If SDAx = 0, set BCLxIF and release SDAx and SCLx.
If SDAx is low, a bus collision has occurred (i.e., another
master is attempting to transmit a data ‘0’; see
Figure
reloaded and begins counting. If SDAx goes from
high-to-low before the BRG times out, no bus collision
occurs because no two masters can assert SDAx at
exactly the same time.
If SCLx goes from high-to-low before the BRG times
out and SDAx 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 SCLx and SDAx
are still high, the SDAx pin is driven low and the BRG is
reloaded and begins counting. At the end of the count,
regardless of the status of the SCLx pin, the SCLx pin is
driven low and the Repeated Start condition is complete.
19-31). If SDAx is sampled high, the BRG is
Figure
Cleared in software
T
BRG
 2011 Microchip Technology Inc.
19-32).
Interrupt cleared
in software
‘0’
‘0’
‘0’