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Wanted: DEC VT05 Font Pictures or ROM Dump

K

kgober

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I've spent the past few days searching the web for information about the DEC VT05 screen font. Either a dump of the character generator ROM, or even clear pictures of what the characters look like on-screen. I found only one decent picture (on these forums, actually!) but it doesn't show all the characters.

Does anyone have a ROM dump from a DEC VT05? Failing that, is there anyone out there with a working VT05 who's willing to put it into Local mode, type the following characters on-screen, then post a clear, in-focus, high-resolution photo of what they look like? ("high resolution" meaning here "high enough that I can clearly identify individual pixels and reconstruct what the ROM would have contained")

Chars.JPG
(the last character in the picture isn't actually a character, it's the cursor)

This is for a VT05 terminal emulator I'm working on (a companion project to the VT52 emulator I recently posted on GitHub).

(also seeking a high-resolution photo of a Teletype Model 37 extended typebox with greek characters for a similar reason, although in this case I can manage without by looking at scanned images of old Unix man pages.)

-ken
 
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My image is from the "ROM" I guessed at by looking at a lot of pictures of VT05's, and squinting a lot. It's an example of a compact layout that shows all the characters in a small space (to make it easier to get a good photo).

But there are some characters that did not appear on any printout, so I have no idea what they should look like (esp. Q). And some characters were too fuzzy for me to be sure I was getting them right. In any event, my image should not be considered "source material" since it did not come from a real VT05.

-ken
 
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Unfortunately they are not the same.

The VT52 has a 128-character 7x8 font, with each character displayed in a 9x10 cell. The VT05 has a 64-character 5x7 font, displayed within a 6x10 cell.

-ken
 
There are at least three different posters of operational VT05 videos on Youtube so you could ask them directly, apart from that I am out of ideas :)
 
Hi Ken,

Schematics on Bitsavers indicate an off-the-shelf National MM5240AA character ROM. You can find the part described starting on page 99 of the databook at:

http://bitsavers.trailing-edge.com/components/national/_dataBooks/1972_National_MOS_Integrated_Circuits.pdf

Here's the character bitmaps from page 102 of that databook, for convenience:

Screen Shot 2017-11-26 at 11.49.44 PM.jpg

Hope this helps!

P.S. Similarly, the LA30 uses an TI 4013 off-the-shelf char gen, it is detailed with bitmaps on page 14-183 or the databook at http://http://bitsavers.trailing-edge.com/components/ti/_dataBooks/1971_TI_IntegratedCircuits/14.pdf

P.P.S. Note the lack of a slash through the zero above. That would be unusual for a data terminal, and on your picture below it looks like the zeros are slashed. I note that the VT05 calls out the part with suffix "AA0" -- maybe this was a ROM with a slashed zero?
 
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It looks like the characters in the NatSemi standard AA ROM are for the 1963 version of ASCII without lowercase and with up- and left-arrows in place of caret (^) and underscore (_). Perhaps the AA0 part substituted caret and underscore in accordance with 1968 ASCII, and while they were at it they put a slash in the zero?

The VT05 Reference Manual makes it pretty clear that the VT05 uses 1968 ASCII, and all the photographs I've seen of VT05 screens indicate that the zero was indeed slashed. Here's the clearest picture I have:
IMG_0726.jpg

So there is still some question about whether DEC used a standard ROM (albeit different from the one shown in the NatSemi databook) or their own custom ROM but either way this is helpful information and it gives me some more leads to work on.
 
Double checked the reference on the schematic -- it is MM5240AM (the "AA0" mentioned earlier was a mistake). It seems National had a series of pre-fab parts with different fonts/encodings available, but the individual data sheets are hard to find...

The one other datasheet I could find had the font pictured below. It has slashed zero and underscore, but also some other differences in letter shapes (at-sign, pound-sign W, etc.). So for total accuracy, I guess you need to get a comprehensive picture of the real thing, or find the definitive datasheet for MM5240AM?

Screen Shot 2017-11-28 at 4.37.36 PM.jpg
 
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I'm not sure the AM would have had a public datasheet, I suspect that designates one of many "customer specific ROMs" for which the customer already knows the content.

The other font is for a vertical-scanning ROM meant for applications where raster scan lines are vertical (e.g. dot matrix printers where characters are rendered left-to-right rather than top-to-bottom like a CRT).

A good picture of the screen may be the best I can hope for. Maybe someday somebody will put up a non-working VT05 for sale that I can pick up and extract the ROM from. (non-working because I'm sure I wouldn't be able to afford the price for a working VT05).
 
I know this is an old posting... But it seems that you are right about the differences in characters.

I have this character ROM in my VT05, the MM5240AA0/J 229
Not sure which brand it is... Maybe someone recognises it?

IMG_20190429_230656.jpg

It gives these characters:

IMG_20190504_143916.jpg

But according the National MM5240AA datasheet the characters look like these:

MM5240AA characterset.jpg

I wonder if an MM5240AA of another brand can have slightly different characters?

Regards, Roland
 
Thanks for the screenshot, it looks like it has everything except @ and I was able to update my emulator accordingly. In particular I was able to update 7, Q, ', &, ^, : and . which I didn't have exactly right.

The National datasheet very clearly indicates that customers may specify their own character sets and I'm confident that DEC did so, so the VT05 version of the MM5240 will have a custom font instead of the default.
 
Sorry, indeed I forgot the @

IMG_20190504_225914.jpg

It seems hard for my phone to get a sharp picture of the
characters with the tinted screen in front of the crt...

Is your emulator a terminal program? I'm curious :)
 
Yes, it's a terminal emulator. It's based on my VT52 terminal emulator (available at https://github.com/kgober/VT52 ) but with the VT05 font and screen size instead. It's still a work in progress, and I haven't yet decided whether it will eventually become a sub-mode of the VT52 emulator, or remain a separate program.
 
I think for now this is going to need to remain a separate program, so I have gone ahead and posted it here: https://github.com/kgober/VT05

It's far from perfect in its current state, but it's probably good enough for most purposes. There are a lot of details that I don't know how to handle accurately, for example the behavior of SHIFT and CTRL when used with keys you normally wouldn't expect (like CTRL-SPACE, SHIFT-0, CTRL-RUBOUT, etc.)

It works at least well enough that you can connect to Unix v5 running on a SIMH-emulated PDP-11, at 300 baud. I suspect there are still problems simulating the need for padding at higher speeds.
 
kgober said:
I think for now this is going to need to remain a separate program, so I have gone ahead and posted it here: https://github.com/kgober/VT05

It's far from perfect in its current state, but it's probably good enough for most purposes. There are a lot of details that I don't know how to handle accurately, for example the behavior of SHIFT and CTRL when used with keys you normally wouldn't expect (like CTRL-SPACE, SHIFT-0, CTRL-RUBOUT, etc.)

It works at least well enough that you can connect to Unix v5 running on a SIMH-emulated PDP-11, at 300 baud. I suspect there are still problems simulating the need for padding at higher speeds.
Click to expand...


Well I could do some tests off course. Emulating with the right characters might be interesting.
I've been talking to Oscar about 3D scanning this terminal for replica purposes.
http://www.vcfed.org/forum/showthread.php?69726-VT05-on-OS-8-gt-filler-characters
So with the right characters on a LCD screen in that VT05 housing gives you probably a good VT05 experience.

But I think that is a better topic under the DEC section. Maybe it's a good idea to post
your simulator in that section too. This is under general wanted stuff... I think people don't read here much often...

Regards, Roland
 
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