Introduction
1325
SPNU503C – March 2018
Copyright © 2018, Texas Instruments Incorporated
Serial Communication Interface (SCI) Module
26.1 Introduction
The SCI module is a universal asynchronous receiver-transmitter that implements the standard nonreturn
to zero format. The SCI can be used to communicate, for example, through an RS-232 port or over a K-
line.
26.1.1 SCI Features
The following are the features of the SCI module:
•
Standard universal asynchronous receiver-transmitter (UART) communication
•
Supports full- or half-duplex operation
•
Standard nonreturn to zero (NRZ) format
•
Double-buffered receive and transmit functions
•
Supports two individually enabled interrupt lines: level 0 and level 1
•
Configurable frame format of 3 to 13 bits per character based on the following:
–
Data word length programmable from one to eight bits
–
Additional address bit in address-bit mode
–
Parity programmable for zero or one parity bit, odd or even parity
–
Stop programmable for one or two stop bits
•
Asynchronous communication mode with no CLK pin
•
Two multiprocessor communication formats allow communication between more than two devices
•
Sleep mode is available to free CPU resources during multiprocessor communication and then wake
up to receive an incoming message
•
The 24-bit programmable baud rate supports 2
24
different baud rates provide high accuracy baud rate
selection
•
Capability to use Direct Memory Access (DMA) for transmit and receive data
•
Four error flags and Five status flags provide detailed information regarding SCI events
•
Two external pins: SCIRX and SCITX
NOTE:
SCI module does not support UART Hardware Flow Control. This feature can be
implemented in Software using a General Purpose I/O pin.
26.1.2 Block Diagram
Three Major components of the SCI Module are:
•
Transmitter
•
Baud Clock Generator
•
Receiver
Transmitter
(TX) contains two major registers to perform double buffering:
•
The transmitter data buffer register (SCITD) contains data loaded by the CPU to be transferred to the
shift register for transmission.
•
The transmitter shift register (SCITXSHF) loads data from the data buffer (SCITD) and shifts data onto
the SCITX pin, one bit at a time.
Baud Clock Generator
•
A programmable baud generator produces a baud clock scaled from VCLK.
Receiver
(RX) contains two major registers to perform double buffering:
•
The receiver shift register (SCIRXSHF) shifts data in from the SCIRX pin one bit at a time and
transfers completed data into the receive data buffer.
•
The receiver data buffer register (SCIRD) contains received data transferred from the receiver shift
register