[Coco] How does the cartridge port work, anyway?

[John Donaldson]

Allen,
    I'm surprised at you. It is really simple. The Cart connector has a pin that 
is connected to the NMI (Non Maskable Interrupt) of the 6809 CPU. This interrupt 
is tripped by the Cart's when the COCO is powered up. The software routine 
associated withe the NMI then calls Address C0000 and executes the instructions 
starting at that address. Thus the Cart program then runs.

John Donaldson




________________________________
From: Allen Huffman <alsplace at pobox.com>
To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
Sent: Thu, February 14, 2013 11:03:58 PM
Subject: [Coco] How does the cartridge port work, anyway?

I have wondered this for ages, and thought this might be a good place to ask...

Could someone explain how the CoCo cartridge port works? How are cartridges able 
to show up as memory locations in that final area of the 64K?

And, perhaps, in terms a software guy with little hardware background could 
understand?
-
Allen Huffman - PO Box 22031 - Clive IA 50325 - 515-999-0227 (vmail/TXT only)
Sent from my MacBook.

22nd Annual "Last" Chicago CoCoFEST! April 27-28, 2013. Lombard, IL. 
http://www.glensideccc.com


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