About the 8020-SCP-322
8020-SCP-322 is a Model 300, 1K Deluxe Processor with RAM that is manufactured by Square D. The standard processors in this series include BCD to binary and binary to BCD conversions, master control relay, synchronous shift registers, and immediate I/O updates. The deluxe processors include all of the standard processor features, as well as asynchronous shift registers, four function math (add, subtract, multiply, divide), print, and communications. The communication instructions allow the processor to communicate with other SY/MAX family processors without requiring any special interfacing hardware. The user only needs a direct cable connection.
The processor memory utilization involves relay circuits. Count the number of contact coils and branches in each run in order to determine the memory required for relay circuits. A contact or coil (including latches) and its address number requires just one word of memory. Spaces and connects don’t require words, but branches require one word for each opening branch and one word for each closing branch. The timer requires four words, the counter requires five words, and the data register requires two words. For rack addressing, each rack assigned requires one word of memory, and each slot addressed required one word of memory.
When the key switch is changed from DISABLE OUTPUTS or RUN to any other position, all programmed outputs are turned off and the processor continues to scan user memory setting outputs on or off according to the ladder diagram program in user memory. A few internal diagnostic checks are performed by the processor, including a continuous check, an I/O image and status comparison, and a check of each word for proper parity.
