cbmnut_at_hushmail.com
Date: 2002-10-02 18:07:36
On Wed, 02 Oct 2002 03:04:20 -0700 ruud.baltissen@abp.nl wrote:
>Hallo John,
>
>> Back in the old days, you'd use something like the 74LS682.
>
>or 688
>
Ok I found it, it's exactly the chip I described that I wished I had, cool!
The SN54/74LS682, 684, 688 are 8-bit magnitude comparators. These
device types are designed to perform comparisons between two eight-bit
binary or BCD words. All device types provide P = Q outputs and the LS682
and LS684 have P>Q outputs also.
8-BIT MAGNITUDE
basically if the two 8bit numbers match, the q goes low. The other versions can do greater than as well. You could combine those of course for >= and <. So to answer my question, when both i/o1 and q are low your at the decoded address at $de00. But this is just a pulse and you would need a flipflop to toggle the LED on/off. Cool, I should try making it.. I think people could find some uses for this simple circuit.. of course with the user port this example is pointless right now. But you could add a chip like an ADC or ram and stuff.
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