The devices include two serial communications interface (SCI) modules (SCI-A, SCI-B). The SCI module

supports digital communications between the CPU and other asynchronous peripherals that use the

standard non-return-to-zero (NRZ) format. The SCI receiver and transmitter are double-buffered, and each

has its own separate enable and interrupt bits. Both can be operated independently or simultaneously in

the full-duplex mode. To ensure data integrity, the SCI checks received data for break detection, parity,

overrun, and framing errors. The bit rate is programmable to over 65000 different speeds through a 16-bit

baud-select register.

Features of each SCI module include:

•

Two external pins:

–

SCITXD: SCI transmit-output pin

–

SCIRXD: SCI receive-input pin

NOTE: Both pins can be used as GPIO if not used for SCI.

–

Baud rate programmable to 64K different rates:

•

Data-word format

–

One start bit

–

Data-word length programmable from one to eight bits

–

Optional even/odd/no parity bit

–

One or two stop bits

•

Four error-detection flags: parity, overrun, framing, and break detection

•

Two wake-up multiprocessor modes: idle-line and address bit

•

Half- or full-duplex operation

•

Double-buffered receive and transmit functions

•

Transmitter and receiver operations can be accomplished through interrupt-driven or polled algorithms

with status flags.

–

Transmitter: TXRDY flag (transmitter-buffer register is ready to receive another character) and TX

EMPTY flag (transmitter-shift register is empty)

–

Receiver: RXRDY flag (receiver-buffer register is ready to receive another character), BRKDT flag

(break condition occurred), and RX ERROR flag (monitoring four interrupt conditions)

•

Separate enable bits for transmitter and receiver interrupts (except BRKDT)

•

NRZ (non-return-to-zero) forma