About the 8020-SCP-323
8020-SCP-323 is a Model 300, 2K Deluxe Processor with RAM that is manufactured by Square D. The ladder diagram program is supported by a few different types of memory. RAM (Random Access Memory) is volatile and uses batteries. UV PROM (Ultraviolet Programmable Read Only Memory) is non-volatile and requires an ultraviolet light to erase the program. The RAM/UV PROM memory mix has a maximum total memory size of 2K, wherein the maximum total UV PROM memory is 1K. When all processor lights are on, there has been an incorrect power up sequence. When all processor lights are off, there has been a loss of power.
A parity bit is incorporated in each word of user memory, and each word is checked for proper parity. The memory light will turn on and the halt light will flash if there is a parity error fault. The processor compares the status of the I/O image table with the actual status of each input and output within the system at the end of each memory scan. After the outputs have been written to, their status is read back to confirm that they match. Processor operation halts and external outputs turn off if the actual output status does not match the I/O image table.
The addressing format utilizes External Digital I/O, internal relays, and data storage registers. The local digital rack can support 64 digital I/O points and a 2 channel LI module with remote drops. 54.7 ms is the maximum update time for any drop on channel 1. 84 ms is the maximum update time for any drop on channel 2.
