Summary of Contents for NCD Input Scanner RS-232
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Page 1: Users Guide
8SC RS-232 Input Scanner Users Guide Revision 1 .0 B y R y a n S h e l d o n Copyright © 1 996, 1 997, 1 998, 1 999, 2000, National Control Devices... -
Page 2: Special Thanks
Disclaimer: NCD will not be responsible for any personal injury or damage to computers or other electronic devices caused in conjunction with the use of NCD products. The user assumes full responsibility of any and all damage that may result in combination with NCD products, services, and literature. NCD takes EVERY known precaution to ensure documentation and examples are accurate. - Page 3 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.
- Page 4 When data is received by the computer from the 8SC, each pin that is connected to ground will return a unique number. Example: When no inputs are tied to ground, RN2 pulls all inputs high. This returns a 255. When input 1 is the only line connected to ground, a 254 will be returned (255-1, 1 is the weight of input 1). When input 4 is the only line connected to ground, a 247 will be returned (255-8, 8 is the weight of input 4).
- Page 5 Inputs D0-D7 are pulled up via RN2 4.7K resistor network. 74LS251 Data Inputs Care should be taken when interfacing to the inputs of this device. Remember, inputs are pulled high and are activated when they are connected to ground. Debugging: Basic checks: Verify all chips are located and oriented in the proper location.
- Page 6 The NCD-110C Interface Processor and How It Works: The NCD-110C is a PIC-based computer that has been programmed to listen to incoming data on the serial port and to respond ONLY if its name is called. To understand how it works, we will examine the processes of the 110C as they were written into the chip. The NCD-110C carefully listens to incoming data on an RS-232 serial port.
- Page 7 Copyright © 1 996, 1 997, 1 998, 1 999, 2000, All Rights Reserved. Amiga is a registered trademark of Commodore Business Machines. IBM is a registered trademark of International Business Machines. Macintosh is a registered trademark of Apple Computer.