IBM RS-232 manual Interfacing to the Serial Port of Your Computer

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Helpful hint.

Could cause problems later under normal operation.

Fatal mistake.

The X tells about common assem- bly and operation errors as well as other things to watch out for.

The check is a guide to help the user with assembly and operation. Use them to prevent mistakes.

WARNING:

NEVER ASSEMBLE ANY NCD DEVICE WITH ORGANIC OR

ACID CORE SOLDER. USING THESE TYPES OF SOLDER WILL

VOID ALL NCD WARRANTIES.

Interfacing to the Serial Port of Your Computer

The NCD-8SC requires the NCD-RSB for interfacing to computers. The RSB is required because it is capable of converting an open-collector RS-232 transmission to a standard RS-232 signal that can be used by your computer. All NCD devices that transmit data back to a computer use an open-collector transmission. The open-collector system is important because it allows many devices to send data to your computer without using extensive logic circuits to "OR" together incoming data. If you are not familiar with "OR"ing data, you should know that the process can be complicated, especially for RS-232 trans- missions. The open-collector system allows us to use 3 wires to connect 16 devices. One wire is a ground that must be shared among all devices on the serial port. Another wire, the transmit (Tx) line, sends data to NCD devices. Some NCD devices send data back to the computer using a third line (receive or RX). Since the 8SC transmits data back to the computer, the receive line must be connected to read the transmissions.

See the NCD-RSB manual for interfacing the 8SC to your computer. This manual will assume you have an RSB connected to your system.

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Contents 8SC RS-232 Input Scanner Users Guide Special Thanks Introduction and OverviewWhat You Will Need Interfacing to the Serial Port of Your Computer Input 4 is weighted by Debugging NCD-110C Interface Processor and How It Works NCD-110C Addressing74LS251 Input Multiplexer