PIC16F87 Datasheet, PDF (105/214 Pages) Microchip Technology – 18/20/28-Pin Enhanced FLASH Microcontrollers with nanoWatt Technology

PIC16F87/88
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 11.1 “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 11-2:
ASYNCHRONOUS MASTER TRANSMISSION
Write to TXREG
BRG Output
(Shift Clock)
RB5/SS/TX/CK pin
TXIF bit
(Transmit Buffer
Reg. Empty Flag)
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 11-3:
ASYNCHRONOUS MASTER TRANSMISSION (BACK TO BACK)
Write to TXREG
BRG Output
(Shift Clock)
RB5/SS/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 11-7: 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 GIE
10Bh,18Bh
PEIE TMR0IE INTE RBIE TMR0IF INTF R0IF -000 000x -000 000u
0Ch
PIR1
—
ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF -000 0000 -000 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
—
ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE -000 0000 -000 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.
 2003 Microchip Technology Inc.
Preliminary
DS30487B-page 103