Re: 1551 Repair - 28 pin 6523 Wanted

From: Gerrit Heitsch <>
Date: Sat, 08 Mar 2014 23:40:52 +0100
Message-ID: <>
On 03/08/2014 11:34 PM, Jim Brain wrote:
> I'm awaiting a few 5V XC9536-10 (yep, actual 5V Xilinx logic CPLD) ICs,
> and am hopeful to try it out.  I need to test and see if the unused bits
> on the 6523T databus read as  0, or are truly undefined.

They are probably open pads on the die which is either a 6525 or 6523 
die in a 28pin DIP. So they should behave as open Pins on a normal I/O 
chip. If set to input in the DDR they should read as '1' and if set to 
output in the DDR, they should read back as whatever you wrote into the 
output register.

So in other words, define the full 6523 and then just package it as a 
6523T. Would also mean that we'd have the 6523/6525 in the 1551 covered 
as well. :)


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Received on 2014-03-08 23:00:43

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