PIC16F87XA Datasheet, PDF (118/234 Pages) Microchip Technology – 28/40/44-Pin Enhanced Flash Microcontrollers

PIC16F87XA
When setting up an Asynchronous Transmission,
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 “USART Baud
Rate Generator (BRG)”).
2. Enable the asynchronous serial port by clearing
bit SYNC and setting bit SPEN.
3. If interrupts are desired, then set enable bit TXIE.
4. If 9-bit transmission is desired, then set transmit
bit TX9.
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).
8. If using interrupts, ensure that GIE and PEIE
(bits 7 and 6) of the INTCON register are set.
FIGURE 10-2:
Write to TXREG
BRG Output
(Shift Clock)
RC6/TX/CK (pin)
TXIF bit
(Transmit Buffer
Reg. Empty Flag)
ASYNCHRONOUS MASTER TRANSMISSION
Word 1
Start Bit
Bit 0
Bit 1
Word 1
Bit 7/8 _{Stop Bit}
TRMT bit
(Transmit Shift
Reg. Empty Flag)
Word 1
Transmit Shift Reg
FIGURE 10-3:
ASYNCHRONOUS MASTER TRANSMISSION (BACK TO BACK)
Write to TXREG
BRG Output
(Shift Clock)
RC6/TX/CK (pin)
TXIF bit
(Interrupt Reg. Flag)
Word 1 Word 2
Start Bit
Bit 0
Bit 1
Word 1
Bit 7/8 Stop Bit ^{Start Bit}
Bit 0
Word 2
TRMT bit
(Transmit Shift
Reg. Empty Flag)
Word 1
Transmit Shift Reg.
Word 2
Transmit Shift Reg.
Note: This timing diagram shows two consecutive transmissions.
TABLE 10-5: REGISTERS ASSOCIATED WITH ASYNCHRONOUS TRANSMISSION
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, INTCON
10Bh,18Bh
0Ch
PIR1
GIE
PSPIF⁽¹⁾
PEIE TMR0IE INTE
ADIF RCIF TXIF
RBIE TMR0IF INTF R0IF 0000 000x 0000 000u
SSPIF CCP1IF TMR2IF TMR1IF 0000 0000 0000 0000
18h
RCSTA SPEN RX9 SREN CREN — FERR OERR RX9D 0000 -00x 0000 -00x
19h
TXREG USART Transmit 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 transmission.
Note 1: Bits PSPIE and PSPIF are reserved on 28-pin devices; always maintain these bits clear.
DS39582B-page 116
 2003 Microchip Technology Inc.