Program changeable sequence controller

A program input device for a programmable sequence controller having controller memory means capable of removably containing at least one read-only memory for storing a sequence program comprising a series of instructions, each of the instructions comprising an operation code and address information, input means for selecting external inputs connected thereto in accordance with the instructions, operation control means for examining the selected external inputs in accordance with the instructions, and output means for selectively operating external outputs connected thereto in accordance with the instructions and with the results of the examinations performed by the operation control means, the program input device comprising:

• a read-write memory capable of storing the sequence program,
• connecting means connectible to a read-only memory,
• program transfer means connected to the read-write memory and to the connecting means and connectible to the controller memory means and to a data line of the sequence controller for transferring the sequence program from the read-only memory contained in the controller memory means to the read-write memory in a first transfer mode and from the read-write memory to the read-only memory connected to the connecting means in a second transfer mode,
• program changing means for changing the sequence program stored in the read-write memory, and
• mode changing means selectively switchable to the first and second transfer modes for operating the program transfer means in one of the first and second transfer modes.