Re: 6530 replacement

From: Gerrit Heitsch <>
Date: Tue, 08 Oct 2013 19:14:27 +0200
Message-ID: <>
On 10/08/2013 07:03 PM, Gerrit Heitsch wrote:
> 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?

Ok... Forget that part with RAM, I did misread the data sheet, but while 
the datasheet is unclear in some respects, to me it looks like you need 
to have RS0 = HIGH to read the ROM and LOW for RAM and I/O. Your circuit 
has that inverted.


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Received on 2013-10-08 18:02:10

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