Oric Microdisc: Master/Slave selection

If you want to ask questions about how the machine works, peculiar details, the differences between models, here it is !
How to program the oric hardware (VIA, FDC, ...) is also welcome.
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Oric Microdisc: Master/Slave selection

Post by Dbug » Sun Mar 10, 2019 2:15 pm

I know that the Microdisc controller in theory supports up to 4 devices, which is confirmed by the Microdisc user manual:
Le lecteur MASTER (A) a un cable plat qui sort de l'arrière du boitier, et qui va sur l'ORIC. Les lecteurs esclaves sont livrés avec un cable plat et une prise femelle sur la face arrière, comme l'unité MASTER, mais celle-ci constitue la prise d'entrée. Le cable plat comporte une prise AMPHENOL à chaque extrémité et une prise mâle sertie sur le cable: Pour brancher le lecteur B, on relie la prise arrière du lecteur B à la prise arrière du lecteur A . Pour brancher les suivants (C et D), on relie l'entrée du lecteur suivant à la prise mâle du cable du lecteur précédent. Le schéma ci-dessous est plus explicite sur ce sujet.

Les alimentations fournies peuvent suffire pour une unité centrale et 2 unités de disquettes. Pour un plus grand nombre de lecteurs, il faudra une alimentation supplémentaire, suivant le schéma ci-dessous.
which quickly google-translated gave us this:
The MASTER drive (A) has a flat cable coming out of the back of the box, and going on the ORIC. Slave drives come with a flat cable and a socket on the back, like the MASTER unit, but this is the input socket. The flat cable has an AMPHENOL socket at each end and a male plug on the cable: To connect the reader B, connect the rear socket of the reader B to the rear socket of the reader A. To connect the following (C and D), connect the input of the next reader to the male plug of the cable of the previous reader. The diagram below is more explicit on this subject.

Supplied power supplies may be sufficient for one CPU and 2 floppy disk drives. For a larger number of readers, additional power will be required, following the diagram below.
system_layout.jpg
There are no other details, so I'm wondering if the slave cables (which I don't have) have some magic cable twisting, or if we are supposed to play with jumper switches on the drives?

I've open my own slave drive, I'm just not quite sure how to do that :)

Basically, since I'm going to do a lot of floppy wrangling, testing, formating, copying, I've to make sure I have a fully functional master + slave setup.
(Ideally, master + slave + HxC slave would be awesome, but I'm not there yet, I'm not even sure how to select the unit number on the HXC...)

Here are the photos:
3inch_slave_drive.jpg
3inch_jumpers.jpg

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Re: Oric Microdisc: Master/Slave selection

Post by Symoon » Sun Mar 10, 2019 2:25 pm

Dbug wrote:
Sun Mar 10, 2019 2:15 pm
There are no other details, so I'm wondering if the slave cables (which I don't have) have some magic cable twisting, or if we are supposed to play with jumper switches on the drives?
I think you need to set the drives. I recall buying a second-hand stock, someone that had 3 or 4 drives for his telestrat, and they clearly were sticked as "B", "C" or "D".
Dbug wrote:
Sun Mar 10, 2019 2:15 pm
Basically, since I'm going to do a lot of floppy wrangling, testing, formating, copying, I've to make sure I have a fully functional master + slave setup.
(Ideally, master + slave + HxC slave would be awesome, but I'm not there yet, I'm not even sure how to select the unit number on the HXC...)
HxC manual has all details to be setup, according to which machine and which cable (twisted or not) you use. I took me a moment but in the end I managed to make is work with another drive.
Dbug wrote:
Sun Mar 10, 2019 2:15 pm
3inch_jumpers.jpg
On my Jasmin drive, IIRC the left jumpers were the ones to change (sorry for being vague, but I'm away from my hardware right now).
Jumper set on the most left pins was drive A, going right set it as B. Maybe it depends on the models?
I will try to confirm that as I see it' doesn't seem to match what you got on the photo.

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Re: Oric Microdisc: Master/Slave selection

Post by Chema » Sun Mar 10, 2019 5:22 pm

The controller supports several drives, I can confirm that from my clone. It follows the Shuggart specification, which means that the drive, from 0 to 3, is selected with a signal in the bus. A flat cable is used.

The drive should have a set of jumpers or DIP switches to configure it as ds0-3. I found a manual for a model which is not exactly yours, but could help https://archive.org/details/HitachiHFD305S

I think that the S stands for single headed and the D for double headed? Anyway other similar models, such as the SX did not have the left set of jumpers, but retain the right set:
http://www.retrocomputing.net/parts/h/h ... 018670.JPG

So I bet that one is the one you are looking for and DS0, the first one, is selected.

What I would do is set the Microdisc with one drive and check it works. I'd bet the jumper is in the position in the picture, meaning it is configured as DS0, drive A. You can quite safely plug a second one changing the jumper to the next position and check. When booting, if both are set as DS0 both will start reading and turn in their LEDs. If not, trying to change the drive in Sedoric with B-, or C-, or D- will tell you how it is configured.

I've had two 3,5 drives incorrectly configured and it did not harm the controller or the Oric, so I'd say it is quite safe to test...but that is up to you.

HxC has switches to achieve this and it is well documented.

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Re: Oric Microdisc: Master/Slave selection

Post by Dbug » Sun Mar 10, 2019 5:28 pm

Ha cool, thanks for the PDF, I did search the reference but did not come up with anything!

And I guess that should help me figure out how many drives I can put on the PSU, I stopped using the original Oric one that was starting to ZZZZzzzzzz loudly, so I replaced it by a small Switching PSU that does +5VDC/2A +12VDC/2A

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Re: Oric Microdisc: Master/Slave selection

Post by Chema » Sun Mar 10, 2019 5:44 pm

Yeah, but the jumper/switch area is different :(

Again, my guess is that it is the right 4 jumper set what you are looking for. Moreover when the second picture shows a much similar drive with the left set completely removed. Worth a try.

I don't think you could damage the drive.

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Re: Oric Microdisc: Master/Slave selection

Post by mikeb » Sun Mar 10, 2019 8:59 pm

FYI: The cable-partial-twisting thing was mostly only used on PCs, where the Shugart spec was slightly bodged/ignored, and it meant that you jumpered both drives the same -- the twist in the cable swapped over the drive selects/motor on lines between drive A and B.

In the process, it meant you couldn't have a third and fourth drive on that cable, as there were no longer enough lines (having mangled the wiring around).

From memory, the Shugart connector has one common "Motor On" line and four independent "Drive Select" lines (DS0 to DS3).

Some drives could be jumpered to Motor-On whenever the Motor-On line was asserted (leading to multiple drives rotating at once). Others would Motor-On only when selected. It usually took a bit of fiddling to get the jumpers right. This was in the days where there was an absolute pincushion of pin-options down the back of a drive.

When it got to a four way switch, or just "plug and play, what jumper?" it got simpler.

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Re: Oric Microdisc: Master/Slave selection

Post by iss » Mon Mar 11, 2019 10:46 am

Attached is some info about connecting more drives. Hope it's helpful.
fdd.zip
(1002.16 KiB) Downloaded 15 times

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Re: Oric Microdisc: Master/Slave selection

Post by Chema » Mon Mar 11, 2019 5:26 pm

Aha... look at what it says in the first document (Microdisc 1)
dip.png
dip.png (8.58 KiB) Viewed 437 times
So I am even more convinced that the right set of pins are for configuring the drive number.

Thanks for this iss, it is a very interesting doc. Maybe worth to be stored on the DF library, don't you think Dbug?

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Re: Oric Microdisc: Master/Slave selection

Post by Dbug » Mon Mar 11, 2019 8:58 pm

I guess it would not hurt to extend the library to the purely digital files :)

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Re: Oric Microdisc: Master/Slave selection

Post by Symoon » Mon Mar 11, 2019 10:31 pm

I checked my Jasmin drive: only got one set of 8 pins. And as for other drives, jumper on the left = drive A, sliding to the right gives B, C or D.

About ISS files: they are CEO-Mag extracts. I suspect it would not hurt putting them online (especially if they already were online elsewhere!), but maybe it would be nicer to ask CEO board first?

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Re: Oric Microdisc: Master/Slave selection

Post by Chema » Thu Mar 21, 2019 7:20 pm

Did you manage to get it working, Dbug?

Keep us informed :)

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Re: Oric Microdisc: Master/Slave selection

Post by Dbug » Thu Mar 21, 2019 7:27 pm

Chema wrote:
Thu Mar 21, 2019 7:20 pm
Did you manage to get it working, Dbug?

Keep us informed :)
I had a few busy weekends, did not really touch my Oric last week :)

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