Re: Two 1541-II drives with problems

From: Rob Eaglestone <robert.eaglestone_at_gmail.com>
Date: Tue, 22 Apr 2014 13:00:04 -0500
Message-ID: <CABNTyr9UGFu0UrQherWQaS7RW0pjSyTdOABvYxd2PO=nKoK_Fg@mail.gmail.com>
Makes me wonder what it would take to put most of the 1541 logic onto a
FPGA or CPLD... using SystemVerilog, for example.

(And is my mentioning that considered a proof of my insanity?


On Tue, Apr 22, 2014 at 12:14 PM, Gerrit Heitsch
<gerrit@laosinh.s.bawue.de>wrote:

> On 04/22/2014 06:49 PM, Ville Laustela wrote:
>
>>
>> Hi.
>>
>> Thanks Spiro, that program sounds like a great idea.
>>
>> I made a test over ZoomFloppy (from WinVICE) and the drive 1 of the two
>> drives.
>>
>> I typed in the program and run it and the first run gives "73,CBM DOS
>> V2.6 1541,00,00" and the following runs give "00, OK,00,00". So it appears
>> that the fault must lie at the DC VIA or the S.O bit on the 6502 (can I
>> check this with a logic probe?).
>>
>
> Well, the SO-Bit needs to change state when the drive is running and the
> DOS has enabled that functionality through CA2 of the VIA that controls the
> drive. It is supposed to indicate that a Byte is ready to be read. That
> doesn't mean that the 6502 is reacting to it though, that part happens
> inside the CPU where you cannot reach with a logic probe...
>
> You should grab the schematics for the 1541 long board. That one doesn't
> have the gate array, it does everything in discrete TTL which makes it much
> easier to find out HOW it's done.
>
>  Gerrit
>
>
>
>
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>


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Received on 2014-04-22 18:01:46

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