PIC18F258 Datasheet, PDF (190/384 Pages) Microchip Technology – High Performance, 28/40-Pin Enhanced FLASH Microcontrollers with CAN

PIC18FXX8
FIGURE 18-2:
ASYNCHRONOUS TRANSMISSION
Write to TXREG
BRG Output
(Shift Clock)
RC6/TX/CK (pin)
TXIF bit
(Transmit Buffer
Register Empty Flag)
Word 1
START bit
bit 0
bit 1
Word 1
TRMT bit
(Transmit Shift
Register Empty Flag)
Word 1
Transmit Shift Reg
bit 7/8 _{STOP bit}
FIGURE 18-3:
Write to TXREG
BRG Output
(Shift Clock)
RC6/TX/CK (pin)
TXIF bit
(Interrupt Reg. Flag)
ASYNCHRONOUS TRANSMISSION (BACK TO BACK)
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.
Note: This timing diagram shows two consecutive transmissions.
Word 2
Transmit Shift Reg.
TABLE 18-6: REGISTERS ASSOCIATED WITH ASYNCHRONOUS TRANSMISSION
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 0000 0000 0000 0000
RCSTA SPEN
RX9 SREN CREN ADDEN FERR OERR RX9D 0000 000x 0000 000x
TXREG USART Transmit Register
0000 0000 0000 0000
TXSTA CSRC
TX9 TXEN SYNC — BRGH TRMT TX9D 0000 -010 0000 -010
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.
DS41159B-page 188
Preliminary
 2002 Microchip Technology Inc.