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Pin description – Rainbow Electronics AT75C220 User Manual

Page 74

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AT75C220

74

USART: Universal Synchronous/Asynchronous Receiver/Transmitter

The AT75C220 provides two identical full-duplex, universal
synchronous/asynchronous receiver/transmitters as
USART A and USART B. These peripherals sit on the APB
bus but are also connected to the ASB bus (and hence
external memory) via a dedicated DMA.

The main features are:
• Programmable baud rate generator

• Parity, framing and overrun error detection

• Line break generation and detection

• Automatic echo, local loopback and remote loopback

channel modes

• Multi-drop mode: address detection and generation

• Interrupt generation

• Two dedicated peripheral data controller channels

• 6-, 7- and 8-bit character length

• Modem control signals

Figure 15. USART Block Diagram

Pin Description

Each USART channel has external signals as defined in Table 22.

Peripheral Data Controller

Receive

Channel

Transmit

Channel

Control Logic

Interrupt Control

Baud Rate Generator

Receiver

Transmitter

AMBA

ASB

APB

USxIRQ

ACLK

ACLK/8

RXD

TXD

SCK

USART Channel

Baud Rate Clock

PIO A

Modem Control

NRTS
NCTS
NRI

NDSR

NDTR

NDCD

Table 22. USART External Signals

Signal Name

Description

Type

SCK

USART Serial Clock. Can be configured as input or output. See US_MR

I/O

TXD

Transmit Serial Data

Output

RXD

Receive Serial Data

Input