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SNIU028A – February 2016 – Revised April 2016
Copyright © 2016, Texas Instruments Incorporated
UART Overview
Chapter 12
SNIU028A – February 2016 – Revised April 2016
UART Overview
UCD3138 has two UART modules capable of independently communicating toward two separate peers.
Having more than one UART module is also especially useful for power supplies than need to
communicate with an isolated section (eg. with the digital PFC controller, or a Power Metering ASIC in
offline AC/DC power supplies) through opto-isolators.
While one UART module is serving communication needs over an isolation barrier, the other UART may
be used for communicating with a HOST or serve debugging needs.
This section provides an overview of these UART modules. Table below contains a brief description of the
UART, lists its significant pins and described interrupts.
Description
The UART module is a universal asynchronous receiver-transmitter that implements the standard
non-return to zero format. The UART module can be used to communicate, for example, through
an RS-232 port or over a K-line.
Pins
SCI_Rx UART receive pin
SCI_Tx UART transmit pin
Interrupts
The UART has three interrupts: transmit, receive, and error. Each interrupt can be individually
enabled.
Features
• 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
• Configurable frame format of 3 to 13 bits per character based on the following:
• Data word length programmable from one to eight bits
• Parity programmable for zero or one parity bit, odd or even parity
• Stop programmable for one or two stop bits
• The 24-bit programmable baud rate supports 224 different baud rates provide high accuracy
baud rate selection
• Four error flags and six status flags provide detailed information regarding UART events
Topic
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Page
12.1
UART Frame Format
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12.2
Asynchronous Timing Mode
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12.3
UART Interrupts
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12.4
Transmit Interrupt
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12.5
Receive Interrupt
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12.6
Error Interrupts
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12.7
UART Registers Reference
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