Datasheet

PIC16F87X
DS30292C-page 102  2001 Microchip Technology Inc.
FIGURE 10-5: ASYNCHRONOUS RECEPTION
When setting up an Asynchronous Reception, follow
these steps:
1. Initialize the SPBRG register for the appropriate
baud rate. If a high speed baud rate is desired,
set bit BRGH (Section 10.1).
2. Enable the asynchronous serial port by clearing
bit SYNC and setting bit SPEN.
3. If interrupts are desired, then set enable bit
RCIE.
4. If 9-bit reception is desired, then set bit RX9.
5. Enable the reception by setting bit CREN.
6. Flag bit RCIF will be set when reception is com-
plete and an interrupt will be generated if enable
bit RCIE is set.
7. Read the RCSTA register to get the ninth bit (if
enabled) and determine if any error occurred
during reception.
8. Read the 8-bit received data by reading the
RCREG register.
9. 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
bit1bit0
bit7/8 bit0STOP
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 0000 0000
18h RCSTA SPEN RX9 SREN CREN — FERR OERR RX9D
0000 -00x 0000 -00x
1Ah RCREG USART Receive Register
0000 0000 0000 0000
8Ch PIE1 PSPIE
(1)
ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE
0000 0000 0000 0000
98h TXSTA CSRC TX9 TXEN SYNC — BRGH TRMT TX9D
0000 -010 0000 -010
99h SPBRG Baud Rate Generator Register
0000 0000 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.