Serial Communications Interface (SCI)
The SCI interrupt logic generates interrupt flags when it receives or transmits a complete
character as determined by the SCI character length. This provides a convenient and efficient
way of timing and controlling the operation of the SCI transmitter and receiver. The interrupt
flag for the transmitter is TXRDY (SCICTL2.7), and for the receiver RXRDY (SCIRXST.6).
TXRDY is set when a character is transferred to TXSHF and SCITXBUF is ready to receive the
next character. In addition, when both the SCIBUF and TXSHF registers are empty, the TX
EMPTY flag (SCICTL2.6) is set. When a new character has been received and shifted into
SCIRXBUF, the RXRDY flag is set. In addition, the BRKDT flag is set if a break condition
occurs. A break condition is where the SCIRXD line remains continuously low for at least ten
bits, beginning after a missing stop bit. Each of the above flags can be polled by the CPU to
control SCI operations, or interrupts associated with the flags can be enabled by setting the
RX/BK INT ENA (SCICTL2.1) and/or the TX INT ENA (SCICTL2.0) bits active high.
Additional flag and interrupt capability exists for other receiver errors. The RX ERROR flag is
the logical OR of the break detect (BRKDT), framing error (FE), receiver overrun (OE), and
parity error (PE) bits. RX ERROR high indicates that at least one of these four errors has
occurred during transmission. This will also send an interrupt request to the CPU if the RX ERR
INT ENA (SCICTL1.6) bit is set.
SCI Summary
Asynchronous communications format
65,000+ different programmable baud rates
Two wake-up multiprocessor modes
Idle-line wake-up & Address-bit wake-up
Programmable data word format
1 to 8 bit data word length
1 or 2 stop bits
even/odd/no parity
Error Detection Flags
Parity error; Framing error; Overrun error; Break detection
Double-buffered transmit and receive
Individual interrupts for transmit and receive
11 - 16 C28x - Communications
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