IBM RS-232 manual Input 4 is weighted by

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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). When input 8 is the only line connected to ground, a 127 will be returned (255-128, 128 is the weight of input 8). When inputs 1 and 4 are connected to ground, a 246 will be returned (1+8 weighted total is 9, so 255-9).

Input 1 is weighted by 1.

Input 2 is weighted by 2.

Input 3 is weighted by 4.

 

See the included program "8SCTESTB.BAS" for an example

Input 4 is weighted by 8.

 

of how to software decode the incoming number to the original

Input 5 is weighted by 16.

 

lines that were turned on or off. Also, many programs have

Input 6 is weighted by 32.

 

been included to decode the 8SC inputs to several desirable

 

 

output types. The method shown is the default method.

Input 7 is weighted by 64.

 

 

 

Input 8 is weighted by 128.

 

 

Input1 Input2 Input3 Input4 Input5 Input6 Input7 Input8 Ground

 

(on) and can be turned off by connecting a wire to the ground line.

 

 

When resistor network RN2 is installed, all inputs are pulled high

To Power Supply Ground

To V+ (9 to 12 Volts)

To NCD-RSB Ground

To NCD-RSB Output

To NCD-RSB Input

J1-J4 - Address Select. These jumpers de-

J5 - Baud Rate Select. In-

J6 - Reserved for future expansion.

fine the device number of the 8SC, allow-

stall this jumper for 1200

Jumper between the left two posts.

ing 16 devices to coexist on a single serial

baud operation; remove for

 

line. See "NCD-110 Addressing" for details.

9600 baud operation.

 

Make sure you NEVER connect the power supply to this device backwards. Doing so will destroy the 78L05 and possibly the PIC. Remember, minimal operation voltage is around 7 volts. Also, verify part orientation before proceeding. Watch for shorted solder connec- tions. Please verify component placement before you continue.

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Contents 8SC RS-232 Input Scanner Users Guide Introduction and Overview Special ThanksWhat You Will Need Interfacing to the Serial Port of Your Computer Input 4 is weighted by Debugging NCD-110C Addressing NCD-110C Interface Processor and How It Works74LS251 Input Multiplexer