Modular type Programmable Logic Controller is configured with up to 64k of memory for application programs. The Programmable Logic Controller is facilitated with serial ports that support serial read or write and Modbus master or slave communications. The Programmable Logic Controller is offered in a compact design that facilitates ease of installation. Modular type Programmable Logic Controller is featured with real-time clock, subroutines, PID control, lash memory, and bumpless program store.