Re: 6530 replacement

From: Gerrit Heitsch <>
Date: Tue, 08 Oct 2013 19:03:07 +0200
Message-ID: <>
On 10/08/2013 06:31 PM, wrote:
> Hallo allemaal,
> I designed and built a 6530 replacement, please see:
> The problem: it doesn't work :( I get five blinks on my 8250LP,
> meaning: error zero page RAM 6530. Please have a look at the
> schematic and maybe you can see if I am overlooking something. Many
> thanks!

Unless I'm reading the datasheet for the 6530 wrong, you also need _RSO 
to select the RAM which will cover some parts of the ROM:

 From the datasheet:

A 64 x 8 static RAM is contained in the MCS6530. It is addressed by
A0-A5 (Byte select), RS0, A6, A7, A8, A9 and, depending on on the number 
of chips in the system, CS1 and CS2.

To me that reads that the RAM will cover parts of the ROM, the location 
depending on a mask programmed matrix. You will then also need to use 
_RS0 in your circuit to select the RAM part of the 6532.

Also.. How is RS0 generated on the PCB? Your circuit assumes that as 
soon as RS0 goes LOW, you can enable the ROM. Is that correct or will 
RS0 go LOW at other times with the CS-Lines inactive then?


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Received on 2013-10-08 18:00:08

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