Peripherals
4.6
Serial Communications Interface (SCI) Module
The F281x and C281x devices include two serial communications interface (SCI) modules. The SCI modules
support 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
LSPCLK
−
Baud rate =
=
,
when BRR ≠ 0
(BRR ) 1) * 8
LSPCLK
,
when BRR = 0
16
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)
150 MHz
Max bit rate +
+ 9.375 106 bńs
2 8
†
Serial port performance is limited by I/O buffer switching speed. Internal prescalers must be adjusted such that the peripheral speed is less
than the I/O buffer speed limit—20 MHz maximum.
77
April 2001 − Revised December 2004
SPRS174L
TI [ TEXAS INSTRUMENTS ]
