Datasheet

PIC16F7X
DS30325B-page 74  2002 Microchip Technology Inc.
Steps to follow when setting 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 (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 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 in
the INTCON register are set.
FIGURE 10-2: ASYNCHRONOUS MASTER TRANSMISSION
FIGURE 10-3: ASYNCHRONOUS MASTER TRANSMISSION (BACK TO BACK)
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,
10Bh,18Bh
INTCON GIE PEIE
TMR0IE INTE RBIE TMR0IF INTF RBIF 0000 000x 0000 000u
0Ch 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
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 the PIC16F73/76; always maintain these bits clear.
Word 1
STOP Bit
Word 1
Transmit Shift Reg
START Bit Bit 0 Bit 1 Bit 7/8
Write to TXREG
Word 1
BRG Output
(Shift Clock)
RC6/TX/CK (pin)
TXIF bit
(Transmit Buffer
Reg. Empty Flag)
TRMT bit
(Transmit Shift
Reg. Empty Flag)
Transmit Shift Reg.
Write to TXREG
BRG Output
(Shift Clock)
RC6/TX/CK (pin)
TXIF bit
(Interrupt Reg. Flag)
TRMT bit
(Transmit Shift
Reg. Empty Flag)
Word 1
Word 2
Word 1
Word 2
START Bit
STOP Bit
START Bit
Transmit Shift Reg.
Word 1
Word 2
Bit 0 Bit 1
Bit 7/8 Bit 0
Note: This timing diagram shows two consecutive transmissions.