A programmable controller includes a main processor connected to I/O and peripheral devices for sequential control thereof in a programmed manner. The main processor is associated with a system memory which stores an operating system for the main processor as well as provides a work area used in the operation thereof. A source instruction memory is provided to store a source program for control of the I/O and peripheral devices. The source program is compiled by the main processor into a program including corresponding reduced instructions and stored in an coprocessor instruction memory. A coprocessor is included to retrieve the instructions from the coprocessor instruction memory to execute the instructions in a pipeline mode and in parallel with the execution of the main processor. A data memory is provided for instruction execution of the coprocessor. The main processor and the coprocessor are operatively interconnected by means of a peripheral controller which has address and data buses associated respectively with the main processor and the coprocessor. The peripheral controller is configured to transfer data directly between the system memory and data memory by a direct-memory access [DMA] prior to the start of the parallel processing and to separate the buses with the main processor from those with the coprocessor upon completion of the DMA data transfer to enable the parallel processing at the main processor and the coprocessor.
