Expansion I/O Address Scheme ???

[Walt Perko]

Hi, 

Exactly what is the scheme of the jumpers on the expansion I/O boards? 

J7 to J1?  

How do they relate to the front panel addresses or simple 8080 addressing?  

I've been poking around the GitHub:  https://github.com/dhansel/Altair8800-IOBus

But I don't see any info on that relationship.  

The 02-Serial-Port is what I'm trying to address.  I have two boards and I want them at 10h/11h (00 010 000 / 00 010 001) and the other at 12h/13h (00 010 010 / 00 010 011) if possible.  

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[David Brunell]

I/O port address selection for all of David Hansel's boards work similarly using a set of inverters and an 8-input AND gate. The J1 through J7 jumpers correspond to A1-A7, respectively. Placing a jumper in the upper position (towards the top of the card) selects the card when the corresponding address line is 1, or 0 when the jumper is in the lower position. For example, to set the base address to 10h, you would set J4 up and the rest down.

[Walt Perko]

Hi, 

Okay, that works when the full explanation is made:  

J7 J6 J5 J4 J3 J2 J1 A0    =  Addressing

A7 A6 A5 A4 A3 A2 A1 A0

0  0  0  1  0  0  0  0     =  10h = 16d

This is what I was looking for in the ReadMe etc.  

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