Digital control system for electronic apparatus

Claim 1

A digital control system for use in electronic apparatus, comprising: master control means arranged within the electronic apparatus containing first operational dat and producing a data signal and a clock signal; a plurality of operational circuit elements arranged within the electronic apparatus and connected to be controlled by said master control means; control bus lines comprising a data signal line and a clock signal line interconnecting said master control means and said plurality of operational cirucit elements, said control bus lines being in a release state upon occurence of a predetermined relationship between said clock signal and data signal; said master control means including means for declaring itself master master of said electronic apparatus upon occurence of said predetermined relationship and an inhibit register for inhibiting said master control means from declaring itself the master and placing said master control means in a slave mode upon receipt of a predetermined data word; and auxiliary master control means arranged external to the electronic apparatus and adapted to be connected to said control bus lines and transmitting second operational data by way of said control bus lines for alternatively controlling said operational circuit elements in place of said master control means and in which said second operational data in said auxiliary master control measn includes said predetermined data word for placing said master control means in said slave mode by transmitting said selected data word to said inhibit register in said master control means by way of said control bus lines, and in which said master control means includes means for returning to a master mode a predetermined time after being placed into the slave mode.