S.Elliott's blog

Explore an AP-64, with and without firmware

There are a lot of AP-64 variants around, so let's explore this clone.  Nexo Distribution sold it to me as "APX-EPROM-1" in March 1988.

First, here's a close look at the firmware socket and booster circuit.


Mysterious origins of the AP-64 EPROM programmer

Last December I posted in Apple II Cards about the utterly bizarre firmware of my APX-EPROM-1 Programmer, a clone of the AP-64e that was sold to me by Nexo Distribution in the 1980s.  The APX firmware changes, depending on which slot it's installed in:



PRINTDCI quick-and-easy ASM printing routine


This short routine makes it easy to print strings from assembly code, or even from the mini-assembler.  (Especially in the Enhanced monitor, which lets you enter ASCII characters using a ` prefix.)



Assemblers like EDASM have a directive called DCI that encodes an ASCII string in such a way that the end of the string can be distinguished by checking its high bit.  The DCI statement converts your string into ASCII bytes so that most characters have the high bit cleared, but the last character has its high bit set.



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