PIC18F4520ESLASHMLQTP datasheet(190/390 Pages) MICROCHIP

Part #	PIC18F4520E/MLQTP

Description	28/40/44-Pin Enhanced Flash Microcontrollers with 10-Bit A/D and nanoWatt Technology

PDF	390 Pages

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Manufacturer	MICROCHIP [Microchip Technology]

Direct Link	http://www.microchip.com

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190 / 390 page

PIC18F2420/2520/4420/4520

DS39631A-page 188

Preliminary

 2004 Microchip Technology Inc.

17.4.7.1

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 17-18).

FIGURE 17-18:

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

PIC18F4520E/MLQTP Datasheet(PDF) 190 Page - Microchip Technology