front panels

From: Jack Peacock <>
Date: Tue Feb 24 18:21:24 1998

Tony wrote:

>> <But surely this is a limitation of the front panel not the processor.
>> <I/O bus cycles can (easily) be generated from an appropriately designed
>> <front panel.
>> Processor. The 8080 CPU does I/O To/From the accumulator which is
>I beg to differ.
>All you have to do is to put the CPU into a wait state, tri-state the
>bus buffers and directly drive the address, data and control lines from
>hardware on the frontpanel controller. You can access memory or I/O ports
>that way.
In other words, make the front panel do a DMA access, either to memory or an
I/O port? That way it doesn't affect the CPU state at all, except the CPU
has to be running in order to handle the DMA grant.
Received on Tue Feb 24 1998 - 18:21:24 GMT

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