
PIC16F87XA
DS39582A-page 116
Advance Information
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.
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.
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.
7.
8.
9.
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)
Rcv Buffer Reg
Reg
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
0Ch
INTCON
GIE
PEIE
TMR0IE
INTE
RBIE
TMR0IF
INTF
R0IF
0000 000x
0000 000u
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
PSPIE
(1)
ADIE
0000 0000
0000 0000
8Ch
PIE1
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:
Note 1:
Bits PSPIE and PSPIF are reserved on 28-pin devices; always maintain these bits clear.
x
= unknown,
-
= unimplemented locations read as '0'. Shaded cells are not used for asynchronous reception.