• Please review our updated Terms and Rules here

Simple, generic 80x24(25) display card

M

MykeLawson

Experienced Member
Joined
Mar 21, 2014
Messages
396
I was going through my list of S-100 board manuals & schematics, looking for a generic 80 charater by 24, or 25, line board. Something simple and generic that used a common Character Generator ROM that has descenders. But came up empty handed. Anyone have any thoughts or suggestions? I'm not looking for anything that has graphics capabilities, or requires a special character ROM, or uses PAL/GAL chips. Just something I can wire up with common off the shelf. albeit vintage, chips. Just another project idea....
 
Isn't there something (still) around for the PIC microcontroller that was quite simple to make?

A serial interface (if I remember correctly)...

I came across my notes the other day when I tidied up a room. I did keep them...

Dave
 
MykeLawson said:
I was going through my list of S-100 board manuals & schematics, looking for a generic 80 charater by 24, or 25, line board. Something simple and generic that used a common Character Generator ROM that has descenders. But came up empty handed. Anyone have any thoughts or suggestions? I'm not looking for anything that has graphics capabilities, or requires a special character ROM, or uses PAL/GAL chips. Just something I can wire up with common off the shelf. albeit vintage, chips. Just another project idea....
Click to expand...
How about this board:

S100 Computers - Console IO Board

S100 Computers
www.s100computers.com

Many S100 users have built this board. It has a generic 80 characters/line display, uses standard VGA output, and also provides a PS2 keyboard input. The Propellor chip it is based on does require programming, which is easily done using a PC.
 
hmb said:
Yes, but the original poster is looking for a board he can "wire up using common off the shelf chips". Used CompuPro PC video boards (and the similar Lomas "Color Magic" board) are not easy to find, and are complex boards to reproduce due to their high chip count and use of multiple PALs.
Click to expand...
The CompuPro design is about as simple as an S100 video card can be. 6845 and character ROMs plus enough to attach to the bus. I thought someone had a similar design that didn't try to include CGA modes but I can't find it.
 
MykeLawson said:
Unfortunately, the CompuPro board has six PAL chips and an EPROM. And I do not have the programming info on them, or anyway to program PAL chips. That is one I have a manual for... oh well
Click to expand...
Copying the design of the CompuPro PC Video board, or the Lomas Color Magic board, would be difficult. For a start, both boards require programming of several obsolete PALs, and the logic design of these PALs was not provided. One member of this forum has been trying for some time to reproduce the Lomas Color Magic board, but his project stalled at the point of being able to reproduce the function of its PALs.

If you want to build a modern and more capable version of the CompuPro PC Video board see:

S100 Computers - VGA Board

S100 Computers Cirrus GD5420 VGA board
www.s100computers.com
This is a VGA display board designed for the S100 bus. It is not a simple board to build, since it requires a surface-mounted VGA controller chip, and programming of a couple of GALs.
 
MykeLawson said:
I was going through my list of S-100 board manuals & schematics, looking for a generic 80 charater by 24, or 25, line board. Something simple and generic that used a common Character Generator ROM that has descenders. But came up empty handed. Anyone have any thoughts or suggestions? I'm not looking for anything that has graphics capabilities, or requires a special character ROM, or uses PAL/GAL chips. Just something I can wire up with common off the shelf. albeit vintage, chips. Just another project idea....
Click to expand...

Do you want it to output to a 15KHz composite sync CRT?
First warning is any 7x9 character generator ROM is long out of production, it would be easier to use an EPROM
You should be able to just lift the design of any Z80 based CRT with a 6845 CRT controller to do this. There is
pretty complete documentation for one under http://bitsavers.org/pdf/romac
or lift the CRT controller from the fergusson big board, which is all discrete

If you REALLY want to find a NOS 7x9 character rom (this is a 5v only part) .. https://www.ebay.com/itm/255226708829
 
As I was digging through my S-100 manuals again, it looks like the IMSAI VIO board supports 80x24, and it only has an EPROM for the character generator and glue logic? EPROMs I can program, once I buy the programmer I want. And the manual has all of the bit pattern stuff for the character codes, true descenders, etc. I'm going to see if I can re-generate the schematic into something easier to read and spend some quality time with the manual. I attached a couple of pics of the start of re-generating the schematics.....
 

Attachments

  • VIOpg1.jpg
    VIOpg1.jpg
    511 KB · Views: 10
  • VIOpg2.jpg
    VIOpg2.jpg
    327.5 KB · Views: 10
A lot of that design is dictated by the available state-of-the-art. For example, 16x2102 SRAMs drawing up to 400 ma. each wouldn't even be considered 5 years later. A single 6116 2Kx8 SRAM would do the job.

Unless you were dead-set on replication, I'd use the VIO as a design guide, not something to be copied.
 
Chuck(G) said:
If you want something easy, consider Grant Searle's project from several years ago. The original, IIRC, was based on an ATMega16.

Click to expand...
That is why I asked exactly what Myke wanted to build.
Is it an S-100 card to talk to a CRT monitor controlled by the S-100 CPU using shared RAM?
Most of the suggestions so far aren't that.
The Romac design was interesting because it handled scrolling the display in hardware. The VIO makes you move
the characters in the buffer SRAM, and as Chuck noted, is ancient. The Big Board I design is slightly newer.
Look at the dozens of video terminal maint manuals on bitsavers with z80's in them for other designs, though
they all are pretty much the same.
 
MykeLawson said:
And I do not have the programming info on them, or anyway to program PAL chips.
Click to expand...

FWIW, those dirt cheap TL866 programmers from China can program GALs, and GALs can emulate most of the older PALs... but of course if you don't have the equations that's still an issue.

Al Kossow said:
Is it an S-100 card to talk to a CRT monitor controlled by the S-100 CPU using shared RAM?
Click to expand...

I've been working on my own design for a memory mapped video card that uses all modern parts and should be reasonably easy to adapt to S-100, but it's still stuck in the "working model on a breadboard" stage so I don't suppose that's much help.

It is definitely worth clarifying what's desired here; if all you want is "terminal-like" text only video the single-chip MCU solutions like @Chuck(G) brings up are a dime a dozen, and should do the job perfectly well for CP/M. The design I was working on is specifically aimed at emulating early memory-mapped video systems like the Polymorphic Systems VTI or the TRS-80's built-in video because they were used for some of the first "computer games" and crude graphics, but this kind of design doesn't really offer much in the way of advantages for purely text applications. Back in the 1970's a memory-mapped system actually saved parts compared to a "full terminal", but with most modern MCUs able to emulate a VT-100 or better with one hand tied behind their backs it seems pretty tempting to go with that if running Wordstar is your priority.
 
Throw something together using an Intel 8275? (Does require DMA or at least memory access, IIRC). But inherently memory-mapped, so you don't need to add RAM to your design.
 
Last edited:
hmb said:
Copying the design of the CompuPro PC Video board, or the Lomas Color Magic board, would be difficult. For a start, both boards require programming of several obsolete PALs, and the logic design of these PALs was not provided. One member of this forum has been trying for some time to reproduce the Lomas Color Magic board, but his project stalled at the point of being able to reproduce the function of its PALs.

If you want to build a modern and more capable version of the CompuPro PC Video board see:

S100 Computers - VGA Board

S100 Computers Cirrus GD5420 VGA board
www.s100computers.com
This is a VGA display board designed for the S100 bus. It is not a simple board to build, since it requires a surface-mounted VGA controller chip, and programming of a couple of GALs.
Click to expand...

Correct. I've even built some well-known brute-force PAL readers used in the pinball/arcade realm and I haven't been successful at reading the 16L8 PALs. The Color Magic also has two 20L10 PALs which I can't read at all. I did follow a trail to Rich Lomas but I've been told he doesn't have any of the original design files.

As to the board itself, it's fully routed and posted on my Github. Naturally it's untested at this point, but the redraw is complete.

I looked quickly at the CompuPro schematic. It uses four different types of PALs -- 16R8 (registered; impossible to read), 14H4 (oddball), 12L6 and 10L8 (both possible). So, off the top of my head, I'd say the PC Video would present the same challenges as a recreation, although maybe the security bits haven't been blown. It really would help if we could get the original equations.
 
Last edited:
Eudimorphodon said:
Did anyone every make a card using these for S-100 that used memory in a different slot? Something tells me the glue for that might be non-trivial. Here's an S-100 card using one, but it not only has its own RAM, it has a dedicated Z80 CPU implementing terminal functions.
Click to expand...
I'm not much of an S-100 fan--Multibus is more my speed for the era.

I suspect a few budget terminals of the time used an 8275 or76. Add some memory and a CPU and you're pretty much most of the way there.
 
You must log in or register to reply here.
Back
Top