
PIC16F946
DS41265A-page 138
Preliminary
2005 Microchip Technology Inc.
FIGURE 11-1:
USART TRANSMIT BLOCK DIAGRAM
FIGURE 11-2:
ASYNCHRONOUS MASTER TRANSMISSION
FIGURE 11-3:
ASYNCHRONOUS MASTER TRANSMISSION (BACK-TO-BACK)
TXIF
TXIE
Interrupt
TXEN
Baud Rate CLK
SPBRG
Baud Rate Generator
TX9D
MSb
LSb
Data Bus
TXREG Register
TSR Register
(8)
0
TX9
TRMT
SPEN
RC6/TX/CK/SCK/
Pin Buffer
and Control
8
SCL/SEG9 pin
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/
TXIF bit
(Transmit Buffer
Reg. Empty Flag)
TRMT bit
(Transmit Shift
Reg. Empty Flag)
SCK/SCL/SEG9
Transmit Shift Reg.
Write to TXREG
BRG Output
(Shift Clock)
RC6/TX/CK/
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.
SCK/SCL/SEG9