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TMS320C242
DSP CONTROLLER
SPRS063B – DECEMBER 1997 – REVISED DECEMBER 1999
36
POST OFFICE BOX 1443
HOUSTON, TEXAS 77251–1443
shadowed bits
Many of the control register bits are described as “shadowed”. This means that changing the value of one of
these bits does not take effect until the current conversion is complete.
serial communications interface (SCI) module
The ’C242 device includes a serial communications interface (SCI) module. 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 the 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
–
Up to 1250 Kbps at 20-MHz CPUCLK
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 (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 the 16-bit peripheral bus. 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.
Figure 11 shows the SCI module block diagram.
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