Master internal modem connector

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sydney
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Master internal modem connector

Post by sydney » Fri Apr 03, 2015 2:44 pm

Ever since my master econet connector adventure I've been wanting to utilise more of the masters internal expansion capabilities. The question I have is does anyone now what kind of plug I need to insert into the modem connector on the master motherboard (pl12)? I've removed the white plastic bit and I can push header pins into it and they seem quite stable.
This should enable me to add another 6522, only 1mhz this time, and maybe move my mmbeeb here freeing up the user port for a mouse. I'd also like to experiment with connecting my raspberry pi to my beeb's and this would make that nice and easy too.
UPURS would stay where it is unless I decide to add econet though I've read econet and mmbeeb don't seem to like each other.
Cheers,
Simon

EDIT: A picture paints a thousand words.
The attachment IMG_20150403_155639.jpg is no longer available
IMG_20150403_155752.jpg

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sweh
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Re: Master internal modem connector

Post by sweh » Fri Apr 03, 2015 4:47 pm

Interesting idea. The diagram at http://mdfs.net/Info/Comp/BBC/Circuits/ ... aster2.gif shows the pinout; there's 8 data lines (on the 'B' bus, whatever that means!) and 4 address lines and a few other interesting lines, including 5V...

The master reference manual part1 says (page F.6-9) that &FE80 is "Third party hardware (typically a modem) - 1 Mhz", so if that _is_ the right location then it should be pretty simple to hook up a 6522 to it and gain 2 additional user ports (simpler than what I did for my 2nd User port project 'cos you won't need to decode the 1Mhz bus addresses). I've proven that UPURS will work nicely with that board (my own UPURSFS code has the ability to define alternate base ports at compile time).

Nice!
Rgds
Stephen

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Re: Master internal modem connector

Post by BeebMaster » Fri Apr 03, 2015 7:01 pm

That's not the modem connector, it's the SCSI connector for the Master AIV SCSI interface.

The SCSI board doesn't have a proper connector, it's basically just a load of bare wires:

http://www.beebmaster.co.uk/Domesday/SCSI2.html

Incidentally, not all Masters have that connector. Some have no connector at all, others have a set of header pins.
Image

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Re: Master internal modem connector

Post by RobC » Fri Apr 03, 2015 8:19 pm

BeebMaster wrote:That's not the modem connector, it's the SCSI connector for the Master AIV SCSI interface.
I think it's both the modem connector and the AIV SCSI connector. The circuit diagram has PL12 marked as being for the modem (complete with ~MODEM signal) but I guess that Acorn then hijacked it for the AIV.
BeebMaster wrote:Incidentally, not all Masters have that connector. Some have no connector at all, others have a set of header pins.
Yes - out of the 6 Masters I've got, 3 have it and 3 don't...

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Re: Master internal modem connector

Post by 1024MAK » Fri Apr 03, 2015 10:18 pm

Looking at the schematic, the /MODEM is the chip select signal. It comes from the Acorn Custom I/O controller chip on sheet 1.

Mark

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Re: Master internal modem connector

Post by BeebMaster » Sat Apr 04, 2015 4:04 pm

RobC wrote:
BeebMaster wrote:That's not the modem connector, it's the SCSI connector for the Master AIV SCSI interface.
I think it's both the modem connector and the AIV SCSI connector. The circuit diagram has PL12 marked as being for the modem (complete with ~MODEM signal) but I guess that Acorn then hijacked it for the AIV.
Sometimes I struggle to understand Acorn's thought processes, maybe we all do, it's as if the conversation in the Acorn board room went like this:

CURRY: Great news, Herm! We're putting a 32016 inside the new Project B, and we'll have a modem in it as well! We're gonna call it the Master Scientific Pandora Viewdata Interflora Online!! It's gonna be great, every science lab and flower shop in Britain will have one!
HAUSER: Wait a minute Chris! Philips just Telexed asking how we're doing with our controlling software and hardware interface for their laserdisc player!
CURRY: Holy Harald Hardrada, I'd clean forgotten all about that! Chuck out that pile of 32016s, we'll put a 65C102 on instead and shove a SASI board down the side in the space reserved for leaking battery acid!
HAUSER: OK, while you do that, I'd better get on to Hugo and tell him we need a read-only ADFS which supports 324MB disc sizes and can decrypt 8-bit data stored in sound-waves by tomorrow morning!
CURRY: Right! And somebody had better have a word with the bods at Ordnance Survey and make sure they can get those 35,000 digitised maps of the British isles done asap!
HAUSER: Better tell Roger to do that...
Image

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Re: Master internal modem connector

Post by CMcDougall » Sat Apr 04, 2015 7:00 pm

modem connector is at back right:
eco.JPG
the one pictured in opening thread is for the internal co-pro
ImageImageImage

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Re: Master internal modem connector

Post by 1024MAK » Sat Apr 04, 2015 7:36 pm

Erm, have a look here.

PL12 is the one we are talking about, the white one on the left hand side of the board right near the edge. The adjacent black socket (SK2) is the internal Tube for internal second processors.

There is an audio connector (PL10) for the MODEM somewhere on the board, but I forget where.

That's a nice picture of an econet board Col. 8) Are you trying to say the MODEM audio connector is near the econet board?

Edit: ahh, found PL10. It's next to the speaker plug (PL9) near the front cart socket.

Mark

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Re: Master internal modem connector

Post by CMcDougall » Sat Apr 04, 2015 7:44 pm

^don't know Mark :? , my Master is still being a f!"@£in ...... pain :lol:
:wink:
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Re: Master internal modem connector

Post by RobC » Sun Apr 05, 2015 7:38 am

Just to confirm that the internal modem and AIV SCSI interface share the same space, VFS looks for the SCSI interface at &FE80 (from the disassembly at MDFS) and the Master Reference manual part 1 says this about &FE80:

"Third party hardware (typically a modem) - 1MHz".

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Re: Master internal modem connector

Post by sydney » Wed Jan 27, 2016 4:34 pm

I finally got round to having a go at this and here are the results so far:
20160127_162657.jpg
20160127_162649.jpg
Not had a chance to test it yet but it's very similar to my econet 6522 from a couple of years ago so there shouldn't be a problem (other than my soldering). I'll need to cover the back with some kind of insulator as it's right next to the psu and very exposed. My master is in bits at the moment and I need a new battery pack so it might be a couple of weeks by the time I get round to testing it. I'm planning to add an sd card adapter to port b and use port a for communicating with a raspberry pi or an arduino.

I'm going to post in the MMBEEB or MMFS thread about how to correctly connect this up to an sd card adapter.

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Re: Master internal modem connector

Post by 1024MAK » Wed Jan 27, 2016 6:57 pm

I look forward to reading your posts (hopefully with good results) :D

Do however check where you have done the track cuts to ensure there are no bits of copper that could short between tracks. If I find any, I use a sharp craft knife (the type with snap off blades) to tidy it up.

Mark

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sydney
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Re: Master internal modem connector

Post by sydney » Tue Feb 02, 2016 8:02 pm

Everything is soldered up and my first test was to see if 5v was getting the the sdcard adapter - and it is!
Next I'm going to write a small test program to toggle CB1,CB2,PB0 and PB1 as these are the only signals I'm using. If that is succesful I'm going to need an mmbeeb rom with the base address for the user port changed to the address for the MODEM port.

I presume duikkie's smart spi will work with this and so should MMFS once the address is changed and I'm sure the source code is around here somewhere. Off to search for it.

I probably won't get this done tonight but I have the whole day off tomorrow!

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Re: Master internal modem connector

Post by hoglet » Tue Feb 02, 2016 8:21 pm

sydney wrote: I presume duikkie's smart spi will work with this and so should MMFS once the address is changed and I'm sure the source code is around here somewhere. Off to search for it.
MMFS source is here:
https://github.com/hoglet67/MMFS

Here's a build that includes a Master version (MAMMFS2) that moves the via to &FE80:
mmfs_1_18_20160202_2014.zip
(598.28 KiB) Downloaded 62 times
Dave

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sydney
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Re: Master internal modem connector

Post by sydney » Tue Feb 02, 2016 8:23 pm

Why thank you sir!
I'm off to put the kids to bed and say hello to the wife! I'll report on this in the morning.

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Re: Master internal modem connector

Post by sydney » Wed Feb 03, 2016 11:24 am

I've ran a small test program which should turn pb0 to pb7 on for half a second then off for half a second. Measuring the voltage it is at a constant 5v whether the pin is meant to be on or off. I've not looked at cb1 or cb2 yet. When I attach the sd card board the voltage drops to 2.45v. Off to check my soldering.
Is there anyway to check that &FE80 is the correct address using only a multimeter?
I might also see if DaveH has any more 6522's.

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hoglet
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Re: Master internal modem connector

Post by hoglet » Wed Feb 03, 2016 12:05 pm

sydney wrote: Is there anyway to check that &FE80 is the correct address using only a multimeter?
I've just put a scope on IC15 pin 37 (nMODEM) and it responds to addresses in the range &FE80-&FE9F.

What does the following program show, with and without the board attached?

Code: Select all

10 FOR A%=&FE80 TO &FE9F
20 B%=?A%
30 C%=?A%
40 D%=?A%
50 PRINT ~A%,~B%,~C%,~D%
60 NEXT
Dave

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sydney
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Re: Master internal modem connector

Post by sydney » Wed Feb 03, 2016 1:45 pm

Every time I ran the program I got different results.
Results are for the master by itself, the master with the 6522 board and the master with 6522 board and sdcard board.
I'm going to take a break then look at everything again from the start.
EMPTY

Code: Select all

FE80		5E	5E	5E	
FE81		5E	5E	5E	
FE82		1E	1E	1E	
FE83		1E	5E	5E	
FE84		5E	5E	5E
FE85		5E	5E	5E	
FE86		5E	5E	5E	
FE87		5E	1E	5E	
FE88		1E	1E	1E		
FE89		1E	1E	1E		
FE8A		1E	1E	1E		
FE8B		5E	5E	5E	
FE8C		5E	5E	5E		
FE8D		5E	1E	1E	
FE8E		5E	5E	5C	
FE8F		5E	5E	6E	
FE90		1E	1E	1E	
FE91		5E	5E	5E	
FE92		5E	6E	5E	
FE93		1E	1E	1E	
FE94		5E	5E	1C	
FE95		1E	1E	1C	
FE96		5E	5E	5E	
FE97		5E	5E	1E	
FE98		5E	1E	1E	
FE99		5E	5E	1C	
FE9A		1C	1E	16	
FE9B		5E	5E	5E	
FE9C		1E	1E	1E	
FE9D		1E	1E	1C		
FE9E		5E	5E	5E	
FE9F		5E	7E	5C	
6522 BOARD

Code: Select all

FE80		1C	8	8
FE81		18	18	5C
FE82		18	18	5C
FE83		18	8	8
FE84		5C	5C	5C
FE85		5C	58	58
FE86		18	1C	1C
FE87		18	8	18
FE88		8	18	1C	
FE89		58	58	5C	
FE8A		5C	1C	18	
FE8B		5C	58	5C
FE8C		5C	5C	5C	
FE8D		58	5C	5C
FE8E		48	5C	5C
FE8F		5C	5C	48
FE90		5C	5C	5C
FE91		1C	1C	8
FE92		58	58	58
FE93		8	8	0
FE94		5C	58	58
FE95		8	0	8
FE96		8	8	8
FE97		40	7E	5C
FE98		48	58	5C
FE99		0	1C	18
FE9A		0	8	8
FE9B		7C	5C	5C
FE9C		58	5C	58
FE9D		5C	1C	58
FE9E		8	8	C
FE9F		8	8	0
6522 BOARD + SDCARD BOARD

Code: Select all

FE80		0	0	8
FE81		0	8	8
FE82		8	0	8
FE83		0	48	40
FE84		48	48	58
FE85		5C	58	4C
FE86		7E	4C	5C
FE87		8	0	8
FE88		40	60	48
FE89		5C	5C	48
FE8A		5C	7E	5E
FE8B		1C	7E	8
FE8C		C	6	18		
FE8D		5C	5C	60
FE8E		44	C	18
FE8F		1C	7C	1C
FE90		0	1C	C
FE91		0	0	8
FE92		8	C	3C
FE93		0	C	8
FE94		0	C	8
FE95		48	5C	5C
FE96		40	48	5C
FE97		C	8	8
FE98		58	8	C
FE99		0	C	66
FE9A		5C	48	58
FE9B		8	C	8
FE9C		5C	5C	48
FE9D		40	5C	48	
FE9E		C	60	0
FE9F		48	48	7C

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hoglet
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Re: Master internal modem connector

Post by hoglet » Wed Feb 03, 2016 1:58 pm

Yes, that doesn't look too correct to me.

The Master on it's own is similar to what I see (not exactly the same values), but looks like a floating data bus.

If the 6522 was present and working, I would expect consistent reads, e.g. from FE82 and FE83. That's not the case, so it looks like you are just seeing a differently floating data bus.

I would focus on just the 6522 for now, and ignore the SD Card thingy.

As a simple test, you should be able to write any value to FE82 (DDRB), and then read the same value back again.

Dave

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hoglet
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Re: Master internal modem connector

Post by hoglet » Wed Feb 03, 2016 2:06 pm

Here's something else you could try.

With the machine off, and the multi-meter on a resistance range (e.g. 0-2K), check there is good continuity (< 10 ohms) between:

1. IC22 Pin 22 and your new 6522 pin 22 (R/nW)
2. IC15 Pin 37 and your new 6522 pin 23 (nMODEM)
3. IC22 Pin 23 and your new 6522 pin 25 (1MHz)

Also, make sure you are pulling pin 24 of the 6522 high.

Dave

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sydney
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Re: Master internal modem connector

Post by sydney » Wed Feb 03, 2016 2:17 pm

hoglet wrote:Here's something else you could try.

With the machine off, and the multi-meter on a resistance range (e.g. 0-2K), check there is good continuity (< 10 ohms) between:

1. IC22 Pin 22 and your new 6522 pin 22 (R/nW)
2. IC15 Pin 37 and your new 6522 pin 23 (nMODEM)
3. IC22 Pin 23 and your new 6522 pin 25 (1MHz)

Also, make sure you are pulling pin 24 of the 6522 high.

Dave
I've not done 1,2 or 3 yet as I've just had a quick look at the board and I have pin 23 of the 6522 connected to 5v (pin 18) of the MODEM connector, and pin 24 of the 6522 connected to pin !MODEM (pin 11). Is this my mistake? Off to read my notes.

EDIT: Just read my notes and I think this is the problem! I'll wait for some confirmation before I start desoldering stuff.

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Re: Master internal modem connector

Post by hoglet » Wed Feb 03, 2016 2:24 pm

sydney wrote:
hoglet wrote:Here's something else you could try.

With the machine off, and the multi-meter on a resistance range (e.g. 0-2K), check there is good continuity (< 10 ohms) between:

1. IC22 Pin 22 and your new 6522 pin 22 (R/nW)
2. IC15 Pin 37 and your new 6522 pin 23 (nMODEM)
3. IC22 Pin 23 and your new 6522 pin 25 (1MHz)

Also, make sure you are pulling pin 24 of the 6522 high.

Dave
I've not done 1,2 or 3 yet as I've just had a quick look at the board and I have pin 23 of the 6522 connected to 5v (pin 18) of the MODEM connector, and pin 24 of the 6522 connected to pin !MODEM (pin 11). Is this my mistake? Off to read my notes.

EDIT: Just read my notes and I think this is the problem! I'll wait for some confirmation before I start desoldering stuff.
If you look at the Master's 6522 on the schematic (IC6):
http://mdfs.net/Info/Comp/BBC/Circuits/ ... aster2.gif
you'll see that:
- Pin 23 is the active low chip select
- Pin 24 is the active high chip select connected to +5V.

So I agree you have these the wrong way around.

Dave

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sydney
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Re: Master internal modem connector

Post by sydney » Wed Feb 03, 2016 2:26 pm

In my notes it's the othjer way round. Not sure how I managed to mix them up. I'll report back as soon as I've swithced them over and tested it.

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Re: Master internal modem connector

Post by sydney » Wed Feb 03, 2016 3:14 pm

Still no joy. It looks like the 1mhz signal is not getting to the 6522. I'll try to sort that after the school run. it may not get done until after bedtime for the kids at 8pm tonight though as I have a full day of chores to do before the wife gets home at 5pm!

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Re: Master internal modem connector

Post by sydney » Wed Feb 03, 2016 4:10 pm

OK! PROGRESS!!
There was a small crack in the track where the wire for the 1mhz signal connected to the stripboard, a nice blob of solder sorted that. The 6522 seems to be working correctly now. My test program successully turns pb0 to pb7 on and off every half a second. I now need to test cb1 and cb2 . I'm not using the cheap chinese sdcard boards as I've broken the one I got to use. I'm using one I bought from sirmorris which I'd imagine follows the original wiring. Fortunately it comes with a standard user port connector so I should be able to easily connect it once I figure out which pins are the right ones. I found the following picture on the net but I seem to remember having a conversation with JGH and he said the diagram in the user guide was incorrect for some reason.

Image
The following picture shows how my connector is currently wired.
The attachment 20160203_154842.jpg is no longer available
Here is the back of the board.
20160203_154834.jpg

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Re: Master internal modem connector

Post by hoglet » Wed Feb 03, 2016 4:30 pm

sydney wrote: I found the following picture on the net but I seem to remember having a conversation with JGH and he said the diagram in the user guide was incorrect for some reason.
That looks like it's design for 5V SD Cards (I can't see any level shifters or 3.3V voltage regulator).

You might damage a more modern card!

Dave

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Re: Master internal modem connector

Post by sydney » Wed Feb 03, 2016 4:57 pm

hoglet wrote:
sydney wrote: I found the following picture on the net but I seem to remember having a conversation with JGH and he said the diagram in the user guide was incorrect for some reason.
That looks like it's design for 5V SD Cards (I can't see any level shifters or 3.3V voltage regulator).

You might damage a more modern card!

Dave
I've been using them for a couple of years so the cards i'm using right now are ok. I'll bare that in mind if I need to change cards though.
I've just adapted my 6522 test program to work on the user port at &FE60 and have been able to confirm the wiring for the connector to the sdcard board is correct which means I need to test CB1/CB2 as the last problem to overcome. Back to the housework - she'll be in soon! :shock:

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Re: Master internal modem connector

Post by sydney » Wed Feb 03, 2016 5:53 pm

Another broken track fixed and it works! :D
20160203_175018.jpg
Thanks for all your help Dave.

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Re: Master internal modem connector

Post by IanS » Wed Feb 03, 2016 5:56 pm

hoglet wrote:
sydney wrote: I found the following picture on the net but I seem to remember having a conversation with JGH and he said the diagram in the user guide was incorrect for some reason.
That looks like it's design for 5V SD Cards (I can't see any level shifters or 3.3V voltage regulator).
The diodes are 3.3V zeners to clamp the signals.

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Re: Master internal modem connector

Post by hoglet » Wed Feb 03, 2016 7:26 pm

IanS wrote: The diodes are 3.3V zeners to clamp the signals.
Thanks for clarifying that. I hadn't come across these boards before (before my time I guess....). Did Charlie sell them?
sydney wrote:Another broken track fixed and it works! :D
20160203_175018.jpg
Brill - glad it's working for you now. =D> =D> =D>

Dave

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