Datasheet

 2003-2013 Microchip Technology Inc. DS30491D-page 241
PIC18F6585/8585/6680/8680
To set up an asynchronous transmission:
1. Initialize the SPBRG register for the appropriate
baud rate. If a high-speed baud rate is desired,
set bit BRGH (see Section 18.1 “USART Baud
Rate Generator (BRG)”).
2. Enable the asynchronous serial port by clearing
bit SYNC and setting bit SPEN.
3. If interrupts are desired, set enable bit TXIE.
4. If 9-bit transmission is desired, set transmit bit
TX9. Can be used as address/data bit.
5. Enable the transmission by setting bit TXEN
which will also set bit TXIF.
6. If 9-bit transmission is selected, the ninth bit
should be loaded in bit TX9D.
7. Load data to the TXREG register (starts
transmission).
If using interrupts, ensure that the GIE and PEIE bits in
the INTCON register (INTCON<7:6>) are set.
FIGURE 18-6: ASYNCHRONOUS RECEPTION
TABLE 18-6: REGISTERS ASSOCIATED WITH ASYNCHRONOUS RECEPTION
Start
bit
bit 7/8
bit 1bit 0
bit 7/8 bit 0Stop
bit
Start
bit
Start
bit
bit 7/8
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.
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
INTCON GIE/GIEH PEIE/GIEL
TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 0000 000x 0000 000u
PIR1 PSPIF
ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 0000 0000 0000 0000
PIE1 PSPIE
ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 0000 0000 0000 0000
IPR1 PSPIP
ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 1111 1111 1111 1111
RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 0000 000x 0000 000x
RCREG USART Receive Register 0000 0000 0000 0000
TXSTA
CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 0000 0010 0000 0010
BAUDCON
—RCIDL— SCKP BRG16 — WUE ABDEN -1-1 0-00 -1-1 0-00
SPBRGH Baud Rate Generator Register, High Byte 0000 0000 0000 0000
SPBRG Baud Rate Generator Register, Low Byte 0000 0000 0000 0000
Legend: x = unknown, – = unimplemented locations read as ‘0’. Shaded cells are not used for asynchronous reception.
18F8680.book Page 241 Tuesday, January 29, 2013 1:32 PM