The B873-012 and B875-012 are analog input modules and can be used with 984 Programmable Controllers. The only difference between the two modules is that the B873-012 has four input channels and the B875-012 has eight input channels.

Both modules accept inputs of -10 to +10 volt analog signals. The input is converted to a numerical value, ranging from 0001 to 8191. Values of 0000 or 8192 indicate invalid data. (Refer to the Data Value Reference Chart.) The value is directly proportional to the input signal. For example, an input voltage of -5V causes the module to send a value of 2048. If the input signal goes to 5 V, the module sends a value of 6144. (Refer to Input to Output Data Conversion Chart.)

The PLC polls the module and places the values into input registers (30XXX) designated by the programmer.

Each time the module is powered up, it performs diagnostic tests, resets the input latches, and, for each channel, presents a value of 0000 to the controller. The value is present for approximately three seconds after power up. The module will then start converting the inputs according to the schedule found in the Throughput Rate Section.