Patent US 4,131,835

A microprogrammable control unit has a microprogram which comprises a plurality of command words and which is stored in a memory. The addresses of the command words are stored in an address register which is connected to the memory. The control unit also includes means, comprising decoders, for producing control signals for controlling a switching unit and multiplexers forinterrogating conditions of the switching unit. A control stage is supplied with command words to switch through a plurality of binary characters of a command word to the decoders when a given first binary character in a command word has a first binary value and which switches through a plurality of binary characters of thecommand word to selector inputs of the multiplexers when the given first binary character has a second binary value, and which switches through the command word as an address to the address register when a given second binary character in the preceding command word has a predetermined binary value.