Importance

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Abstract

In a microprogram-controlled device operable under the control of a microprogram, a control storage device (10) comprises a control storage unit (11) memorizing a plurality of microinstructions each including a plurality of every second microinstruction addresses in number less than the maximum number of available branches for the microprogram. A bank switching unit (12) selects, as a selected microinstruction (SMI), one of the next microinstructions on the basis of a branch information signal (BI). A microinstruction register (13) holds the selected microinstruction as a current microinstruction. A branch control unit (15) processes a branch condition signal (BCD), a branch control signal (BCT), a branch classification signal (BCF), and a branch condition selection signal (BCS) into the branch information signal, an address selection signal (AS), and an address modifying signal (AM). An address selector (16) selects, as a selected microinstruction address (SMIA), one of the every second microinstruction addresses on the basis of the address selection signal. An address modifier (17) modifies the selected microinstruction address into a modified microinstruction address (MMIA) on the basis of the address modifying signal and an address modifying selection signal (AMS). The address modifier supplies an address register (14) with the modified microinstruction address.

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First Claim