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PIC16F193X Datasheet, PDF (320/418 Pages) Microchip Technology – 28/40/44-Pin Flash-Based, 8-Bit CMOS Microcontrollers with LCD Driver and nanoWatt Technology | |||
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PIC16F193X/LF193X
22.6.13.2 Bus Collision During a Repeated
Start Condition
During a Repeated Start condition, a bus collision
occurs if:
a) A low level is sampled on SDA when SCL goes
from low level to high level.
b) SCL goes low before SDA is asserted low,
indicating that another master is attempting to
transmit a data â1â.
When the user releases SDA and the pin is allowed to
float high, the BRG is loaded with SSPADD and counts
down to zero. The SCL pin is then deasserted and
when sampled high, the SDA pin is sampled.
If SDA is low, a bus collision has occurred (i.e., another
master is attempting to transmit a data â0â, Figure 22-32).
If SDA is sampled high, the BRG is 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 â1â during the Repeated Start condition,
see Figure 22-33.
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 22-33: BUS COLLISION DURING A REPEATED START CONDITION (CASE 1)
SDA
SCL
RSEN
Sample SDA when SCL goes high.
If SDA = 0, set BCLIF and release SDA and SCL.
BCLIF
S
SSPIF
Cleared by software
â0â
â0â
FIGURE 22-34:
BUS COLLISION DURING REPEATED START CONDITION (CASE 2)
TBRG
TBRG
SDA
SCL
BCLIF
RSEN
S
SSPIF
SCL goes low before SDA,
set BCLIF. Release SDA and SCL.
Interrupt cleared
by software
â0â
DS41364A-page 318
Preliminary
© 2008 Microchip Technology Inc.
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