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Old 13th Apr 2018, 1:40 pm   #1
Slothie
Octode
 
Join Date: Apr 2018
Location: Newbury, Berkshire, UK.
Posts: 1,287
Question MK14 schematic revisions

I'm in the process of making a replica MK14 (I know its been done before, but I've always wanted one and I'm using the exercise to learn/practice how to use Kicad). I've been comparing the schematics for the V1 and V5 boards I found on the interweb, and the main difference seems to be the circuit driving the PROM enable pin. Originally it was tied to A11, but now it's using the once spare NAND gate of IC17 to NAND the "RDS or WDS" line with the inverted A11 signal. This means that a Write to PROM space will enable the PROM outputs causing both the SC/MP and the PROM to drive the data bus.

OK, so before any time the A11 line was 0 this happened too, so I don't see how this is an improvement. I could understand if they gated with the RDS only, or am I missing something obvious?

Anyhow as a newbie on the forum I'd like to say hi and I'm enjoying reading through posts here!

Slothie
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