PIC16F871 Microchip Technology Inc., PIC16F871 Datasheet - Page 63

• Manufacturer Part Number: PIC16F871
• Description: 28/40-pin, 8-bit Cmos Flash Microcontrollers
• Manufacturer: Microchip Technology Inc.

9.0
The Universal Synchronous Asynchronous Receiver
Transmitter (USART) module is one of the two serial
I/O modules. (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
integrated circuits, serial EEPROMs, etc.
REGISTER 9-1:
 2003 Microchip Technology Inc.
ADDRESSABLE UNIVERSAL
SYNCHRONOUS
ASYNCHRONOUS RECEIVER
TRANSMITTER (USART)
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
TXSTA: TRANSMIT STATUS AND CONTROL REGISTER (ADDRESS: 98h)
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)
TX9: 9-bit Transmit Enable bit
1 = Selects 9-bit transmission
0 = Selects 8-bit transmission
1 = Transmit enabled
0 = Transmit disabled
SYNC: USART Mode Select bit
1 = Synchronous mode
0 = Asynchronous mode
Unimplemented: Read as '0'
BRGH: High Baud Rate Select bit
Asynchronous mode:
1 = High speed
0 = Low speed
Synchronous mode:
Unused in this mode
TRMT: Transmit Shift Register Status bit
1 = TSR empty
0 = TSR full
TX9D: 9th bit of Transmit Data, can be parity bit
Legend:
R = Readable bit
- n = Value at POR
TXEN: Transmit Enable bit
Note:
R/W-0
CSRC
SREN/CREN overrides TXEN in Sync mode.
R/W-0
TX9
R/W-0
TXEN
W = Writable bit
‘1’ = Bit is set
R/W-0
SYNC
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 TRISC<7:6> have to
be set in order to configure pins RC6/TX/CK and
RC7/RX/DT
Asynchronous Receiver Transmitter.
The USART module also has a multi-processor
communication
detection.
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
U-0
—
as
PIC16F870/871
capability
the
R/W-0
BRGH
Universal
using
x = Bit is unknown
TRMT
R-1
DS30569B-page 61
9-bit
Synchronous
R/W-0
TX9D
address
bit 0