PIC16F87_05 Datasheet, PDF (105/228 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 “AUSART 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:
Write to TXREG
BRG Output
(Shift Clock)
RB5/SS/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 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 INT0IE RBIE TMR0IF INT0IF RBIF 0000 000x 0000 000u
0Ch
PIR1
— ADIF⁽¹⁾ RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF -000 0000 -000 0000
18h
RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 0000 000x 0000 000x
19h
TXREG AUSART Transmit Data Register
0000 0000 0000 0000
8Ch
PIE1
— ADIE⁽¹⁾ 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.
Note 1: This bit is only implemented on the PIC16F88. The bit will read ‘0’ on the PIC16F87.
 2005 Microchip Technology Inc.
DS30487C-page 103