PC87591L datasheet(151/437 Pages) NSC

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Embedded Controller Modules (Continued)

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4.9

UNIVERSAL SYNCHRONOUS/ASYNCHRONOUS RECEIVER-TRANSMITTER (USART)

The USART is a full-duplex synchronous/asynchronous receiver-transmitter that supports a wide range of software program-

mable baud rates and data formats. It handles automatic parity generation and several error detection schemes. DMA trans-

fers are supported to enable fast processor-independent receive and transmit.

4.9.1

Features

●

Full duplex double-buffered receiver-transmitter

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Synchronous operation

●

Asynchronous operation

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Programmable baud rate between CLK/2 and CLK/32768 baud

●

Numerous framing formats

— seven, eight or nine data bits

— one or two stop bits

— odd, even, mark, space or no parity

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Hardware support of parity-bit generation during transmission and parity-bit check during reception

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Interrupt on transmit buffer empty, receive buffer full and receive error conditions with separate enable

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Software-controlled break transmission and detection

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Software-controlled reset, enable/disable

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Internal diagnostic capability

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Automatic error detection

— Parity Error

— Framing Error

— Data Overrun Error

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9-bit Attention mode

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DMA support for transmit and receive with separate enable

4.9.2

Functional Overview

The USART is composed of the following functional units:

●

Transmitter

●

Receiver

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Baud rate generator

●

Control and error detection

Figure 52 shows a block diagram of the USART.

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