PIC16F877ATISLASHSP datasheet(100/234 Pages) MICROCHIP

100 / 234 page

PIC16F87XA

DS39582B-page 98

 2003 Microchip Technology Inc.

9.4.7.1

Clock Arbitration

Clock arbitration occurs when the master, during any

receive, transmit or Repeated Start/Stop condition,

deasserts the SCL pin (SCL allowed to float high).

When the SCL pin is allowed to float high, the Baud

Rate Generator (BRG) is suspended from counting

until the SCL pin is actually sampled high. When the

SCL pin is sampled high, the Baud Rate Generator is

reloaded with the contents of SSPADD<6:0> and

begins counting. This ensures that the SCL high time

will always be at least one BRG rollover count, in the

event that the clock is held low by an external device

(Figure 9-17).

FIGURE 9-18:

BAUD RATE GENERATOR TIMING WITH CLOCK ARBITRATION

SDA

SCL

SCL deasserted but slave holds

DX-1

BRG

SCL is sampled high, reload takes

place and BRG starts its count

03h

02h

01h

00h (hold off)

03h

02h

Reload

BRG

Value

SCL low (clock arbitration)

SCL allowed to transition high

BRG decrements on

Q2 and Q4 cycles

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