
2004 Microchip Technology Inc.
DS30491C-page 229
PIC18F6585/8585/6680/8680
18.0
ENHANCED UNIVERSAL
SYNCHRONOUS
ASYNCHRONOUS RECEIVER
TRANSMITTER (USART)
The Universal Synchronous Asynchronous Receiver
Transmitter (USART) module is one of the two serial
I/O modules. (USART is also known as a Serial
Communications Interface or SCI.) The USART can be
configured as a full-duplex asynchronous system that
can communicate with peripheral devices, such as
CRT terminals and personal computers. It can also be
configured as a half-duplex synchronous system that
can communicate with peripheral devices, such as A/D
or D/A integrated circuits, serial EEPROMs, etc.
The Enhanced USART module implements additional
features, including automatic baud rate detection and
calibration, automatic wake-up on sync break reception
and 12-bit break character transmit. These make it
ideally suited for use in Local Interconnect Network bus
(LIN bus) systems.
The USART can be configured in the following modes:
Asynchronous (full-duplex) with:
- Auto-wake-up on character reception
- Auto-baud calibration
- 12-bit break character transmission
Synchronous – Master (half-duplex) with
selectable clock polarity
Synchronous – Slave (half-duplex) with selectable
clock polarity
In order to configure pins RC6/TX/CK and RC7/RX/DT
as the Universal Synchronous Asynchronous Receiver
Transmitter:
SPEN (RCSTA<7>) bit must be set (= 1),
TRISC<6> bit must be set (= 1), and
TRISC<7> bit must be set (= 1)
.
The operation of the Enhanced USART module is
controlled through three registers:
Transmit Status and Control (TXSTA)
Receive Status and Control (RCSTA)
Baud Rate Control (BAUDCON)
These are detailed on the following pages in
and
respectively.
Note:
The USART control will automatically
reconfigure the pin from input to output as
needed.