[Coco] CoCo floppy disk subsystem

[Arthur Flexser]

P.S.  The full designation of the chip I'm talking about is MB8877A.  Spec
sheet is here:

https://www.digchip.com/datasheets/parts/datasheet/170/MB8877A-pdf.php

It appears to be available for under $10--a lot cheaper than a multipak, if
using a 26-3022 with a CoCo 2 or 3 is the only reason you need a multipak.

Art

On Thu, Jan 14, 2021 at 1:48 PM Arthur Flexser <flexser at fiu.edu> wrote:

> I seem to recall using my 26-3022 controller with a CoCo 2 without a
> multipak.  The reason this worked was presumably that I had had to replace
> the WD1793 controller chip some time previously, and the replacement sent
> to me was a Fujitsu 8877, which I believe doesn't require 12V.
>
> Can anyone confirm this about the Fujitsu chip?
>
> Art
>
> On Thu, Jan 14, 2021 at 1:30 PM John Mautz <ejmautz2 at gmail.com> wrote:
>
>> According to cocopedia.com the 26-3022 is not compatible with the CoCo2
>> or
>> 3 without using a Multi-Pack.
>>
>> http://www.cocopedia.com/wiki/index.php/26-3022
>>
>> The controller is based on the Western Digital WD1793. It features an
>> analog data seperator circuit, infamous for its inherent unreliability and
>> has multiple potentiometers which are used to calibrate various delay and
>> timing features of the disk-side interface. It requires a +12 volt DC
>> supply to operate, and is thus not compatible with a CoCo 2 or 3 unless a
>> Multi-Pak Interface (or other source of +12V) is used or the CoCo or
>> controller are "hacked", also contains the Disk BASIC ROM chip, and the
>> necessary interface logic.
>>
>> Hope you have a multi-pack.
>>
>>
>> On Thu, Jan 14, 2021 at 12:39 PM Salvador Garcia via Coco <
>> coco at maltedmedia.com> wrote:
>>
>> > Happy New Year all. Thanks to Rietveld's exploration with using the
>> GoTek
>> > with a CoCo and other computers, I was motivated to get a GoTek myself
>> to
>> > test my floppy drive subsystem that is not working correctly.
>> >
>> > I have the 26-3022 floppy drive and controller. I had this working back
>> in
>> > the 80s with my CoCo 1. This past December I decided to unpack it all
>> and
>> > give it a run. Much to my dismay, the floppy drive subsystem did not
>> work
>> > as expected. I got as far as getting the formatting process started with
>> > DSKINI 1, but after the head steps 34 times and seeks, I would get the
>> > dreaded IO ERROR.
>> >
>> > Since I was on vacation in Mexico, I decided to bring back with me the
>> > 26-3022 controller (the drive was too cumbersome and heavy).
>> >
>> > My plan is to swap out parts, specifically, the drive and cable, hoping
>> > that the problem is with one of these. I have no way to swap out the
>> cart
>> > controller. I got the GoTek to substitute the floppy drive and I already
>> > ordered and got a new 5.25" drive flat cable, with no twist.
>> >
>> > I received my GoTek yesterday and am in the process of installing the
>> > FlashFloppy firmware. Here is what I have:
>> >
>> > 1. CoCo 2 and 3
>> > 2. 26-3022 cart controller plus original flat cable
>> > 3. New 34 pin flat cable for 5.25" floppy drives (this has one connector
>> > at each end)
>> > 4. 34-pin edge connector to IDC adapter (to connect the 5.25" drive
>> cable
>> > to the GoTek)
>> > 5. GoTek emulator SFR1M44-U100K-R
>> >
>> > Am I able to build a working floppy disk subsystem using these items? Or
>> > asked another way, is the 26-3022 compatible with the CoCo 2 or 3?
>> >
>> > Any tips or advice on building this system?
>> >
>> > As always thank you all for your time and assistance. Salvador
>> >
>> > --
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>> >
>>
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>