PIC18F4539-ESLASHMLSQTP datasheet(165/322 Pages) MICROCHIP

165 / 322 page

 2002 Microchip Technology Inc.

Preliminary

DS30485A-page 163

PIC18FXX39

16.4.17.3

Bus Collision During a STOP

Condition

Bus collision occurs during a STOP condition if:

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

sampled low before SDA goes high.

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 16-31). 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

attempting to drive a data '0' (Figure 16-32).

FIGURE 16-31:

BUS COLLISION DURING A STOP CONDITION (CASE 1)

FIGURE 16-32:

BUS COLLISION DURING A STOP CONDITION (CASE 2)

SDA

SCL

BCLIF

PEN

SSPIF

TBRG

SDA asserted low

SDA sampled

low after TBRG,

Set BCLIF

'0'

SDA

SCL

BCLIF

PEN

SSPIF

TBRG

Assert SDA

SCL goes low before SDA goes high,

Set BCLIF

'0'

PIC18F4539-E/MLSQTP Datasheet(PDF) 165 Page - Microchip Technology

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