PIC16F627A Datasheet, PDF (71/168 Pages) Microchip Technology – FLASH-Based 8-Bit CMOS Microcontrollers

PIC16F627A/628A/648A
12.0 UNIVERSAL SYNCHRONOUS
ASYNCHRONOUS RECEIVER
TRANSMITTER (USART)
MODULE
The Universal Synchronous Asynchronous Receiver
Transmitter (USART) is also known as a Serial Com-
munications Interface or SCI. The USART can be con-
figured as a full-duplex asynchronous system that can
communicate with peripheral devices such as CRT ter-
minals and personal computers, or it can be configured
as a half-duplex synchronous system that can commu-
nicate with peripheral devices such as A/D or D/A inte-
grated circuits, Serial EEPROMs, etc.
The USART can be configured in the following modes:
• Asynchronous (full-duplex)
• Synchronous - Master (half-duplex)
• Synchronous - Slave (half-duplex)
Bit SPEN (RCSTA<7>), and bits TRISB<2:1>, have to
be set in order to configure pins RB2/TX/CK and RB1/
RX/DT as the Universal Synchronous Asynchronous
Receiver Transmitter.
Register 12-1 shows the Transmit Status and Control
Register (TXSTA) and Register 12-2 shows the
Receive Status and Control Register (RCSTA).
REGISTER 12-1:
TXSTA: TRANSMIT STATUS AND CONTROL REGISTER (ADDRESS: 98h)
R/W-0 R/W-0 R/W-0 R/W-0
U-0
R/W-0
R-1
R/W-0
CSRC
TX9
TXEN SYNC
—
BRGH
TRMT
TX9D
bit 7
bit 0
bit 7
CSRC: Clock Source Select bit
Asynchronous mode
Don’t care
Synchronous mode
1 = Master mode (Clock generated internally from BRG)
0 = Slave mode (Clock from external source)
bit 6
TX9: 9-bit Transmit Enable bit
1 = Selects 9-bit transmission
0 = Selects 8-bit transmission
bit 5
TXEN: Transmit Enable bit⁽¹⁾
1 = Transmit enabled
0 = Transmit disabled
bit 4
SYNC: USART Mode Select bit
1 = Synchronous mode
0 = Asynchronous mode
bit 3
Unimplemented: Read as '0'
bit 2
BRGH: High Baud Rate Select bit
Asynchronous mode
1 = High speed
0 = Low speed
Synchronous mode
Unused in this mode
bit 1
TRMT: Transmit Shift Register STATUS bit
1 = TSR empty
0 = TSR full
bit 0
TX9D: 9th bit of transmit data. Can be parity bit.
Note: SREN/CREN overrides TXEN in SYNC mode.
Legend:
R = Readable bit
-n = Value at POR
W = Writable bit
’1’ = Bit is set
U = Unimplemented bit, read as ‘0’
’0’ = Bit is cleared x = Bit is unknown
 2002 Microchip Technology Inc.
Preliminary
DS40044A-page 69