24 Feb
1998
24 Feb
'98
6:21 p.m.
Tony wrote:
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.
<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.