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Browse Prior Art Database

Microprogram Branching Device

IP.com Disclosure Number: IPCOM000078681D
Original Publication Date: 1973-Feb-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 53K

Publishing Venue

IBM

Related People

Chilinski, H: AUTHOR [+3]

Abstract

With microprogram-controlled data-processing systems comprising instruction counters, a test and branch instruction I1 is executed during the control program at the beginning of the instruction phase (I-phase), branching, if required, to an exception routine.

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Microprogram Branching Device

With microprogram-controlled data-processing systems comprising instruction counters, a test and branch instruction I1 is executed during the control program at the beginning of the instruction phase (I-phase), branching, if required, to an exception routine.

By means of the subsequent microinstructions I2, I3, ..., a fresh microinstruction is read from main storage, analyzed, and finally at the end of the I-phase, using a conditional branch instruction, a branch is taken to the corresponding executive phase (E-phase) E1, E2 ... En.

The various E-phases start at positions E11, E21 ... En1, with the microinstructions at the end of the respective E-phases branching, in most cases, by an unconditional branch instruction E1m, E2m ... Enm, and in some cases as a function of a preceding microinstruction "set condition code" to the beginning of the I-phase.

The improvement in microprogram branching consists in the unconditional branch instructions, for branching back E1m- E2m ... Enm as well as several instructions at the beginning of the E-phases, being eliminated entirely.

Fig. 1 shows the block diagram of the improved microprogram branching device, which results in the new control program sequence depicted in Fig. 2. A comparison shows that the following microinstructions are saved over the usual technique. I-Phase Test and branch microinstruction I1. Fetch instruction I2. E- Phase Set condition code instruction.

As is shown in Fig. 2, a...