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PRIMA Steuerwerk (control unit)

PRIMA Steuerwerk (control unit) screenshot


The control unit ('Steuerwerk') of the PRIMA processor. It takes the following inputs:

and generates the control signals for the processor. These are: Unfortunately, the schematics is not (yet) optimized for small screen sizes. Still, several main groups of components are easily distinguished. On the left side is the small sequencer state machine that generates the three states of the PRIMA instruction cycle, namely instruction fetch, address fetch, and execute.

The upper part of the circuit calculates the conditional branch flag used to control the PC multiplexer. The value is based on the current instruction, the current accumulator value (e.g. zero), and the current sequencer state.

The bottom part of the circuit contains the flipflop and logic to manage the overflow flag.

Finally, the flipflop on the right is used to generate a (hazard-free) impulse required for the write-enable signal for the main memory.

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Impressum | 24.11.06