Slogger ROMbox Plus and Printer Port MMFS

[Ukwebb]

I've just tried fitting an SD/MMFS reader into printer port on my Slogger ROMbox Plus and cant get it work beyond "Card?"

Using the same MMFS (v1.55 Jan24) ROM, same wiring, same SD reader and SD card on my Acorn Plus 1 works fine

Which points at either a problem with the ROMbox+ or a simple incompatibility

Has anyone got an SD reader connected to the printer port on a ROMbox+ ?
if so did you have to do anything special?

[hoglet]

Which points at either a problem with the ROMbox+ or a simple incompatibility

Does a schematic exist for the ROMBOX or ROMBOX+?

Dave

[Ukwebb]

Well - Thanks Slogger !!!
Although i cant find a schematic for the rombox- the Acorn one is well documented. trying to compare the two and noticed that there doesnt appear to be any connection to pin19 (ACK) on the slogger like there is on the Acorn one.

however the slogger does a trace on pin21 - which is N/C on the Acorn and on the Schematic.
Surely they cant have messed up an important signal like the Acknowledge pin could they?
Swapped the pin 19 wire onto pin21 and ... yup - it works !

Moral of the story : don't take anything for granted !

This is the Slogger rombox....

and the Acorn plus 1 for comparison

hopefully this may help anyone else in the future too

[hoglet]

Surely they cant have messed up an important signal like the Acknowledge pin could they?
Swapped the pin 19 wire onto pin21 and ... yup - it works !

Moral of the story : don't take anything for granted !

Gosh that is interesting.

It seems Slogger are using the Centronics BUSY signal, rather than the ACK signal:

images.png (22.83 KiB) Viewed 186 times

Both will work I think, with suitably written software.

Tom Seddon has done a disassembly of the Slogger Expansion ROM 2.02 and that certainly expects the printer busy status to be visible on &FC72 bit 7:
https://github.com/tom-seddon/SloggerEl ... .s65#L1437

But nice job figuring this out!

Dave

PS There is more on the differences between ACK and BUSY by MartinB here:
viewtopic.php?p=25585#p25585

[Ukwebb]

Well it's certainly not going to find anything on pin 19 !! Lol

And given that it's working with the elk's mmfs ROM, with no other modifications, I'm going to stick with, they simply wired it up wrong !

Silly slogger !!

(I wonder if there is anyone in here from those slogger days that may remember)

[Pernod]

Tom Seddon has done a disassembly of the Slogger Expansion ROM 2.02 and that certainly expects the printer busy status to be visible on &FC72 bit 7:
https://github.com/tom-seddon/SloggerEl ... .s65#L1437

So presumably this suggests Slogger's use of the BUSY line was intentional?

[hoglet]

Tom Seddon has done a disassembly of the Slogger Expansion ROM 2.02 and that certainly expects the printer busy status to be visible on &FC72 bit 7:
https://github.com/tom-seddon/SloggerEl ... .s65#L1437

So presumably this suggests Slogger's use of the BUSY line was intentional?

I would think so, and I suspect the ROMBOX+ is the same.

Martin B made this observation:

However, it soon became apparent that when using the PC LPT port in DOS or through a command prompt window and therefore bypassing and printer driver, /ACK is not read at all by the PC and all the handshaking is controlled via /STROBE and BUSY alone.

I think both approaches are valid, and a correctly designed printer should provide both signals.

Dave

[1024MAK]

On other micros, for minimal parallel printer ports, the use of just /STROBE and BUSY was more common than using /STROBE and /ACK.

Mark

[Ukwebb]

Not sure if it would affect anything around the SD card etc, but I am using v1.33 of the RH plus 1 16k rom from MDFS.

It's obviously not going to rewire the port, but maybe I should do to make the socket compatible with the acorn one

[danielj]

So far as I can tell from Acorn's application note and the circuit diagrams, BUSY is never connected on the beeb or Master or Plus 1 - just /ACK. I had an old alphacom 42 printer that would work with the beeb but would *never* work properly with the rombox plus. My suspicion is Slogger screwed up but because so few (if any?) printers relied on it they didn't notice. The other bit of evidence is that they designed the Expansion 2.0 ROM to work in the Plus one OR rombox plus. I don't see any attempt to discern whether the ROM's in a Plus one or rombox plus in the code.