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1000-0901, rev 1.1 March 1998 COM232/8AT User’s Guide

Overview

The COM232/8AT eight-channel asynchronous serial communication adapter is designed to be 100

percent compatible with the IBM PC/AT. Eight phone jacks (RJ-11 connectors) are used for making

external connections.

The serial interface is made through eight 16550 Asynchronous Communication Elements (ACEs).

16550 ACEs are compatible with 8250 ACEs used in IBM PC, PC/XT, and compatible computer

models. In addition, the 16550 ACEs are 16450 compatible while offering a FIFO mode. This

additional mode can be invoked to reduce overhead in the CPU. The FIFO mode increases

performance by providing a 16-byte transmit FIFO and one 16-byte receive FIFO. These two FIFOs

buffer data, thereby reducing the number of interrupts issued to the CPU.

Other features of the 16550 ACE include:

⇒

Programmable baud rate, character length, parity, and the number of stop bits.

⇒ Automatic addition and removal of start, stop, and parity bits.

⇒ Independent and prioritized transmit, receive and status interrupts.

Specifications

Bus Interface: IBM compatible 16-bit bus

Dimensions: 8” x 4.8”

Controllers: Eight 16550 Asynchronous Communication Elements

Channels: Eight, numbered 1 through 8

External Connections: Type RJ-11 phone jack connectors

Transmit Drivers: MC1488, or compatible

Receive Buffers: MC1489, or compatible

I/O Address Range: 0000 - FFFF hex

Interrupt Levels: 2 thru 7, 10 thru 12, 14 thru 15

Power Requirements:

Supply

494 mA +5 Volts

56 mA +12 Volts

58 mA - 12 Volts

is the typical adapter current value.

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