MICROPROGRAM CONTROLLER FOR DETECTING THE OCCURRENCE OF AN INTERRUPT REQUEST OR A TERMINATION OF A STRING INSTRUCTION

A microprogram controller receives an interrupt request signal during execution of a STRING instruction for transferring a character-string or a bit string. In the execution of the STRING instruction, a data transmission operation for transferring one unit of the character-string or bit-string is repeated a predetermined number of times, and an instruction end signal is produced after data transfer. The interrupt request signal and the instruction end signal are supplied to an OR gate. By executing a compound conditional branch instruction, the output level of the OR gate is judged. If the output of the OR gate takes an active level, interrupt processing or STRING instruction end processing is executed.