Measurement Computing COM232/8AT - Manual (Page 3)

1000-0901, rev 1.1 March 1998 COM232/8AT User’s Guide 3
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:
I
T
Supply
494 mA +5 Volts
56 mA +12 Volts
58 mA - 12 Volts
I
T
is the typical adapter current value.