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4.8
Serial Communications Interface (SCI) Modules (SCI-A, SCI-B)
Baud rate =
LSPCLK
16
LSPCLK
(BRR
1) * 8
when BRR
≠
0
Baud rate =
when BRR = 0
Max bit rate
100 MHz
16
6.25
10
6
b s
TMS320F2808, TMS320F2806
TMS320F2801, UCD9501
Digital Signal Processors
SPRS230F–OCTOBER 2003–REVISED SEPTEMBER 2005
The 280x 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:
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) format
Ten SCI module control registers located in the control register frame beginning at address 7050h
NOTE
All registers in this module are 8-bit registers that are connected to Peripheral Frame 2.
When a register is accessed, the register data is in the lower byte (7-0), and the upper
byte (15-8) is read as zeros. Writing to the upper byte has no effect.
Enhanced features:
Auto baud-detect hardware logic
16-level transmit/receive FIFO
The SCI port operation is configured and controlled by the registers listed in
Table 4-8
and
Table 4-9
.
Peripherals
65