[sdiy] Reviving an Arp Quadra and interfacing the Intel 8243

Karl Ekdahl elektrodwarf at yahoo.se
Sat Jul 30 02:41:53 CEST 2016

Hi list, first post here in a few years..
So i'm trying to revive my old Arp Quadra again. The original computer was dead and i couldn't find a new one so i wrote an operating system for it back a few years ago. Well it seems that the old MPLAB i used with my PIC isn't really compatible anymore so i'm trying to transfer the code to an Arduino instead since it'll be more portable anyway and i can more easily share it with other folks. But i'm running into some problems interfacing the Intel 8243 I/O Expander chip. In theory it seems really straight forward but for some reason the arduino won't do what the old pic did (and still does) - so i need a bit of a sanity check. The datasheet for the IC can be found here (http://www.cpu-galaxy.at/cpu/ram%20rom%20eprom/other_intel_chips/other_intel-Dateien/8243_Datasheet.pdf) and my thinking for the proper interfacing sequence is as follows:
set PROG HIGH (since the port number is transfered on the first high-to-low transition)
set ~CS HIGH (disable the chip)
set the port address ORed with the 3rd bit HIGH for write modeset ~CS LOW (enable the chip)set PROG LOW (to transfer the port address and instruction)set data to be written to the addressset PROG HIGH (to transfer the data to the port)set ~CS HIGH (to disable the chip from changing output)

everything with the appropriate timing delays of course - am i missing something? This is how i did it in my PIC code and it works but for the life of me it won't work with my arduino....
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