13.5 Multiprocessor and Asynchronous Communication Modes
The SCI has two multiprocessor protocols, the idle-line multiprocessor mode (see
address-bit multiprocessor mode (see
). These protocols allow efficient data transfer between
multiple processors.
The SCI offers the universal asynchronous receiver/transmitter (UART) communications mode for interfacing
with many popular peripherals. The asynchronous mode (see
) requires two lines to interface
with many standard devices such as terminals and printers that use RS-232-C formats. Data transmission
characteristics include:
• One start bit
• One to eight data bits
• An even/odd parity bit or no parity bit
• One or two stop bits
13.6 SCI Programmable Data Format
SCI data, both receive and transmit, is in NRZ (non-return-to-zero) format. The NRZ data format, shown in
• One start bit
• One to eight data bits
• An even/odd parity bit (optional)
• One or two stop bits
• An extra bit to distinguish addresses from data (address-bit mode only)
The basic unit of data is called a character and is one to eight bits in length. Each character of data is formatted
with a start bit, one or two stop bits, and optional parity and address bits. A character of data with its formatting
information is called a frame and is shown in
.
Start
LSB
2
3
Parity Stop
4
5
6
7
MSB
Start
LSB
2
3
Addr/
data
Parity
4
5
6
7
MSB
Stop
Idle-line mode
(Normal nonmultiprocessor communications)
Address-bit mode
Address bit
Figure 13-3. Typical SCI Data Frame Formats
To program the data format, use the SCICCR register. The bits used to program the data format are shown in
.
Table 13-2. Programming the Data Format Using SCICCR
Bit(s)
Bit Name
Designation
Functions
2-0
SCICHAR
SCICCR.2:0
Select the character (data) length (one to eight bits).
5
PARITYENA
(ENABLE)
SCICCR.5
Enables the parity function if set to 1, or disables the parity function if cleared to 0.
6
PARITY
(EVEN/ODD)
SCICCR.6
If parity is enabled, selects odd parity if cleared to 0; even parity if set to 1.
7
STOPBITS
SCICCR.7
Determines the number of stop bits transmitted—one stop bit if cleared to 0 or two stop
bits if set to 1.
Serial Communications Interface (SCI)
SPRUH18I – JANUARY 2011 – REVISED JUNE 2022
TMS320x2806x Microcontrollers
803
Copyright © 2022 Texas Instruments Incorporated
Содержание TMS320 2806 Series
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