PIC18F44J10-ESLASHP datasheet(182/358 Pages) MICROCHIP

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PIC18F45J10 FAMILY

DS39682C-page 180

Preliminary

15.4.14

SLEEP OPERATION

While in Sleep mode, the I2C module can receive

addresses or data and when an address match or

complete byte transfer occurs, wake the processor

from Sleep (if the MSSP interrupt is enabled).

15.4.15

EFFECTS OF A RESET

A Reset disables the MSSP module and terminates the

current transfer.

15.4.16

MULTI-MASTER MODE

In Multi-Master mode, the interrupt generation on the

detection of the Start and Stop conditions allows the

determination of when the bus is free. The Stop (P) and

Start (S) bits are cleared from a Reset or when the

MSSP module is disabled. Control of the I2C bus may

be taken when the P bit (SSPxSTAT<4>) is set, or the

bus is Idle, with both the S and P bits clear. When the

bus is busy, enabling the MSSP interrupt will generate

the interrupt when the Stop condition occurs.

In multi-master operation, the SDAx line must be

monitored for arbitration to see if the signal level is the

expected output level. This check is performed in

hardware with the result placed in the BCLxIF bit.

The states where arbitration can be lost are:

• Address Transfer

• Data Transfer

• A Start Condition

• A Repeated Start Condition

• An Acknowledge Condition

15.4.17

MULTI -MASTER COMMUNICATION,

BUS COLLISION AND BUS

ARBITRATION

Multi-Master mode support is achieved by bus arbitra-

tion. When the master outputs address/data bits onto

the SDAx pin, arbitration takes place when the master

outputs a ‘1’ on SDAx, by letting SDAx float high and

another master asserts a ‘0’. When the SCLx pin floats

high, data should be stable. If the expected data on

SDAx is a ‘1’ and the data sampled on the SDAx

pin = 0, then a bus collision has taken place. The

master will set the Bus Collision Interrupt Flag, BCLxIF

and reset the I2C port to its Idle state (Figure 15-25).

If a transmit was in progress when the bus collision

occurred, the transmission is halted, the BF flag is

cleared, the SDAx and SCLx lines are deasserted and

the SSPxBUF can be written to. When the user services

the bus collision Interrupt Service Routine and if the I2C

bus is free, the user can resume communication by

asserting a Start condition.

If a Start, Repeated Start, Stop or Acknowledge condition

was in progress when the bus collision occurred, the

condition is aborted, the SDAx and SCLx lines are deas-

serted and the respective control bits in the SSPxCON2

collision Interrupt Service Routine and if the I2C bus is

free, the user can resume communication by asserting a

Start condition.

The master will continue to monitor the SDAx and SCLx

pins. If a Stop condition occurs, the SSPxIF bit will be set.

A write to the SSPxBUF will start the transmission of

data at the first data bit regardless of where the

transmitter left off when the bus collision occurred.

In Multi-Master mode, the interrupt generation on the

detection of Start and Stop conditions allows the deter-

mination of when the bus is free. Control of the I2C bus

can be taken when the P bit is set in the SSPxSTAT

cleared.

FIGURE 15-25:

BUS COLLISION TIMING FOR TRANSMIT AND ACKNOWLEDGE

SDAx

SCLx

BCLxIF

SDAx released

SDAx line pulled low

by another source

Sample SDAx. While SCLx is high,

data doesn’t match what is driven

Bus collision has occurred.

Set bus collision

interrupt (BCLxIF)

by the master.

by master

Data changes

while SCLx = 0

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