PIC18F1220ESLASHSSSQTP datasheet(149/308 Pages) MICROCHIP

149 / 308 page

DS39605F-page 147

PIC18F1220/1320

16.3.6.2

Receiving a Break Sync

To receive a Break Sync:

Configure

the

EUSART

for

asynchronous

transmit and receive. TXEN should remain

clear. SPBRGH:SPBRG may be left as is.

Enable auto-wake-up. Set WUE.

Enable RXIF interrupts. Set RCIE, PEIE, GIE.

The controller may be placed in any power

managed mode.

An RCIF will be generated at the beginning of

the Break signal. When the interrupt is received,

read RCREG to clear RCIF and discard. Allow

the controller to return to PRI_RUN mode.

Wait for the RX line to go high at the end of the

Break signal. Wait for any of the following: WUE

to clear automatically (poll), RB4/RX to go high

(poll) or for RBIF to be set (poll or interrupt). If

RBIF is used, check to be sure that RB4/RX is

high before continuing.

Enable Auto-Baud Rate Detect. Set ABDEN.

Return from the interrupt. Allow the primary

clock to start and stabilize (PRI_RUN or

PRI_IDLE).

When the next RCIF interrupt occurs, the

received baud rate has been measured. Read

RCREG to clear RCIF and discard. Check

SPBRGH:SPBRG

for

valid

value.

The

EUSART is ready for normal communications.

Return from the interrupt. Allow the primary

clock to run (PRI_RUN or PRI_IDLE).

10. Process subsequent RCIF interrupts normally

as in asynchronous reception. TXEN should

now be set if transmissions are needed. TXIF

and TXIE may be set if transmit interrupts are

desired. Remain in PRI_RUN or PRI_IDLE until

communications are complete. Clear TXEN and

return to step 2.

FIGURE 16-9:

SEND BREAK CHARACTER SEQUENCE

Write to TXREG

BRG Output

(Shift Clock)

Start Bit

Bit 0

Bit 1

Bit 11

Stop Bit

Break

TXIF bit

TX (pin)

TRMT bit

SENDB

Dummy Write

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