Datasheet

PIC18F2450/4450
© 2008 Microchip Technology Inc. DS39760D-page 153
15.0 ENHANCED UNIVERSAL
SYNCHRONOUS RECEIVER
TRANSMITTER (EUSART)
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 and so on.
The Enhanced Universal Synchronous Receiver
Transmitter (EUSART) module implements additional
features, including Automatic Baud Rate Detection
(ABD) and calibration, automatic wake-up on Sync
Break reception and 12-bit Break character transmit.
These features make it ideally suited for use in Local
Interconnect Network bus (LIN bus) systems.
The EUSART 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
The pins of the Enhanced USART are multiplexed
with PORTC. In order to configure RC6/TX/CK and
RC7/RX/DT as an EUSART:
• bit SPEN (RCSTA<7>) must be set (= 1)
• bit TRISC<7> must be set (= 1)
• bit TRISC<6> must be cleared (= 0) for
Asynchronous and Synchronous Master modes
or set (= 1) for Synchronous Slave mode
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
Register 15-1, Register 15-2 and Register 15-3,
respectively.
Note: The EUSART control will automatically
reconfigure the pin from input to output as
needed.