PIC876 datasheet(104/218 Pages) MICROCHIP

104 / 218 page

PIC16F87X

DS30292C-page 102

 2001 Microchip Technology Inc.

FIGURE 10-5:

ASYNCHRONOUS RECEPTION

When setting up an Asynchronous Reception, follow

these steps:

Initialize the SPBRG register for the appropriate

baud rate. If a high speed baud rate is desired,

set bit BRGH (Section 10.1).

Enable the asynchronous serial port by clearing

bit SYNC and setting bit SPEN.

If interrupts are desired, then set enable bit

RCIE.

If 9-bit reception is desired, then set bit RX9.

Enable the reception by setting bit CREN.

Flag bit RCIF will be set when reception is com-

plete and an interrupt will be generated if enable

bit RCIE is set.

Read the RCSTA register to get the ninth bit (if

enabled) and determine if any error occurred

during reception.

Read the 8-bit received data by reading the

RCREG register.

If any error occurred, clear the error by clearing

enable bit CREN.

10. If using interrupts, ensure that GIE and PEIE

(bits 7 and 6) of the INTCON register are set.

TABLE 10-6:

REGISTERS ASSOCIATED WITH ASYNCHRONOUS RECEPTION

START

bit

bit7/8

bit1

bit0

bit7/8

bit0

STOP

bit

START

bit

START

bit

bit7/8

STOP

bit

RX (pin)

Reg

Rcv Buffer Reg

Rcv Shift

Read Rcv

Buffer Reg

RCREG

RCIF

(Interrupt Flag)

OERR bit

CREN

Word 1

RCREG

Word 2

RCREG

STOP

bit

Note:

This timing diagram shows three words appearing on the RX input. The RCREG (receive buffer) is read after the third word,

causing the OERR (overrun) bit to be set.

Address

Name

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

Value on:

POR,

BOR

Value on

all other

RESETS

0Bh, 8Bh,

10Bh,18Bh

INTCON

GIE

PEIE

T0IE

INTE

RBIE

T0IF

INTF

R0IF

0000 000x

0000 000u

0Ch

PIR1

PSPIF(1)

ADIF

RCIF

TXIF

SSPIF

CCP1IF

TMR2IF

TMR1IF

0000 0000

18h

RCSTA

SPEN

RX9

SREN

CREN

—

FERR

OERR

RX9D

0000 -00x

1Ah

RCREG USART Receive Register

0000 0000

8Ch

PIE1

PSPIE(1)

ADIE

RCIE

TXIE

SSPIE

CCP1IE

TMR2IE TMR1IE

0000 0000

98h

TXSTA

CSRC

TX9

TXEN

SYNC

—

BRGH

TRMT

TX9D

0000 -010

99h

SPBRG

Baud Rate Generator Register

0000 0000

Legend: x = unknown, - = unimplemented locations read as '0'. Shaded cells are not used for asynchronous reception.

Note 1: Bits PSPIE and PSPIF are reserved on PIC16F873/876 devices; always maintain these bits clear.

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