41594B datasheet(255/372 Pages) MICROCHIP

255 / 372 page

 2011-2012 Microchip Technology Inc.

Preliminary

DS41594B-page 255

PIC12LF1840T48A

25.6.13.3

Bus Collision During a Stop

Condition

Bus collision occurs during a Stop condition if:

After the SDA pin has been deasserted and

allowed to float high, SDA is sampled low after

the BRG has timed out.

After the SCL pin is deasserted, 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 SSP1ADD 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 25-37). 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 25-38).

FIGURE 25-38:

BUS COLLISION DURING A STOP CONDITION (CASE 1)

FIGURE 25-39:

BUS COLLISION DURING A STOP CONDITION (CASE 2)

SDA

SCL

BCL1IF

PEN

SSP1IF

TBRG

SDA asserted low

SDA sampled

low after TBRG,

set BCL1IF

’0’

SDA

SCL

BCL1IF

PEN

SSP1IF

TBRG

Assert SDA

SCL goes low before SDA goes high,

set BCL1IF

’0’

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