There are two forms of CP/M experience:
? Small, slow and cramped typical of early floppies of 120 and 241K size.
? High performance using fast large media (hard disks, IDE, CF, SD).

The bulk of CP/M systems I've done are:
Z80
64K ram with eprom overlay for boot, system load, hidden bios,? and utility (256K).
IO as needed to get to the world, dual serial is usual? (SIO or DART, or 8251A)
Maybe a PIO or 8255 PPI
A few include either a timer (8253, or similar) or periodic interrupt.
? Time keeping is not required by CP/M but is useful for applications.
Mass storage
? Over time that was floppy,?
? IDE hard disk? (its not that hard especially if you skip the high byte)?
? Later CF? (does 8bit memory mode nicely still can be found often faer bigger than needed)
? and finally SD? (programming for it is a PITA).

Other storage can be EEprom really slow write but fine for read more
than write and Eprom (read only media) or large RAM (Ram disks).
These can be be ports or part of the main address and mapped in
and out.? Ports using 8255 PPI or LS273 are easier, adding a small
counter (7 bits) can make it easier still.

CP/M wants based on experience larger disks in the 1M to 8MB range.
IF the disk used is larger you partition it in the BIOS (there are other ways)
But a hint do not do all 16 possible devices as you are wasting ram 4 logical
drives is a good working number.? NOTE: CP/M 2 can only address a logical
drive of 128x65536 or 8MB (internal math limit).? Any of the CP/M replacements
P2DOS and later can take that to 1GB however with a flat directory stay at 8mb
and partition for 4 working drives.

Serial or simulated serial IO makes it easier for supporting ported apps to
a system.? Memory mapped video adds parts as it hen has to be mapped
in and out and applications need to stick to standard interfaces and that
can complicate software design.? Its easier if the IO looks like the nominal
console of the day terminal (ADM-3 or VT52, Vt100, H19) or something
that has the feel of TTY (yech!).

FYI if you have larger storage you can remap any drives partition.? Hint?leave
the boot drive as boot drive.? CPM can handle any format but for modern
non floppy that means translating to LBA and then doing sector deblocking
as CP/M assumes 128bytes as logical sector and most modern media is 512.
For that I use 16384 tracks and 4 logical sectors per track (for an 8mb "disk").
That helps with the deblocking code and the "track" is then the LBA address
(Plus any offset for partitioning).? CP/M BIOS math is rather archaine in its
explanation for the disk parameter tables.

As a convenience the system can be loaded from Eprom.? I do that all the time
as it makes the system less dependant on getting it initially on media.? The latter
can be a pain with current system with no support or difficult for that.? CP/M
does not care how it gets in ram (its the job of the bios!).? Even loaded from Eprom
its easy to allow for soft loading from disk as a file.

There is enough free and useful software to fill a large disk!? I have about 18mb
of software I use on the AmproLB+(45MB)? and NS Horizon (32mb) hard disks.

Allison

Not a fan of TMS9918, hard to get too.

As I have a large collection of CP/M base systems...
S100 several... (Altair, NorthStar, Compupro)
AmproLB+
Kaypro 2 and also 4/84
DEC VT180 (z80 board + Vt100)
Osborne portable
Epson PS-8

If one wants to copy classic S100 with front panel do the imsai it was better.
However that died rather fast leaning toward FLoppy based turnkey systems.

Most systems with video or character displays went three ways:
Sinclair ZX80 used the cpu to do it (cheap video), high cpu consumption and only
NTSC, Try to find a monitor.? Also if its small (MC in mint tin) the average 9"
monitor dwarfs it.? Most video systems had upper//lower case.

S100 and friends use either 64Char x 16line (processor tech VDM-1) and similar.
Later ones use 80x24/25? (just more parts).
TRS80 was of the VDM-1 style of 64x16 All upper for base system and later
versions added lower and 80 char.

Epson PS-8 was a 80x8 LCD with 6803 support for the display and random stuff.
Tandy trs80 M100/Koyocera,NEC8200 were all 40char wide by 8 line LCD.

Later ones use SMC5027 or 6545 CTRC chips with all the surrounding glue and
speed parts.

I happen to like a programmed atmega or two (Grant Searle) as it allows for
VGA, PS2 keyboard.

nearly all of the above had chip counts that were not small format friendly.
The most compact and complete is the ELF VT-102? but that needs the
1802 for half the task (ram and DMA refresh).? It also needs atmega for
the PS-2 keyboard.

The above also reflects that if you do video you need a keyboard.
Most common keyboards are now USB.

The alternate path is a 320x240 LCD with a 40 x 20 screen, still need
MPU to make that go.

Allison

Richard Cini wrote:

I do like the VID design, but here are a few things I thought of:

If you don’t have an aversion to using a PLD, a small GAL like a 16V8
might be useful for decoding and would still be period-appropriate.
There are several “new” designs in both the Retrobrew S100 and ECB
designs that use them, and they’re still available online from secondary
suppliers or eBay.

I've used PLDs in other designs for clients. They certainly reduce the parts count, and are good for "get it out the door quick" projects. They're great for commercial products that must fit in a certain size, and to keep your design safe(r) from copycats.

But they don't have the longevity of generic widely-sourced parts. I still have a pile of disk controller boards I can't build because the parts are no longer available.

PLDs also seem less suitable for hobby projects when you *want* people to be able to duplicate it. There are problems finding parts, finding programmers, and writing the equations to program them. They feel like a closed-box solution.

For the RAM, if you don’t need 128k, I might consider something like a
Cypress 32kx8 which is in a 0.300” DIP28 (rather than the normal
0.600”). That saves some space.

Yes, I use them on several of my kits. Once they got used by the millions in early PCs, they became generic. Lots of sources, and still available new.

They enabled another trick: If you look at my 6502 Badge and VIP2K kits, you'll see the 32k 0.3" RAM that hides *under* the 32k 0.6" EPROM. Their pinouts are almost the same, so it's easy to wire up, too.

The reason for the 128K RAM on the Z80-VID was to try to make a CP/M system on two boards. One is the existing CPU board, with Z80, 32K RAM, 32K EPROM, and 8-bit I/O ports. The second is the VID board, with NTSC/PAL video, SPI to run an SD-card for "disk storage", and more RAM so there's enough for 64K for the Z80, plus 20K for the video screen.

Alas, there are still too many parts to fit on a 3.5"x2" card without PALs, surface mount, modern parts, etc. But hope dies hard; maybe there's a way...

Lee Hart
--
A designer knows he has achieved perfection not when there is
nothing left to add, but when there is nothing left to take away.
-- Antoine de Saint Exupery
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com

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Actually, I'm already doing a re-spin of the product, to make it more environmentally robust, use a better A-D converter (the one I'm using now has caused many problems), and fully isolate an RS-485 interface.? I'll still need to produce a limited number of my existing design, in order to support spares for existing installations, but in the future I'll "mass"-produce only the newer version.

So, although it wasn't my original intention, I'll see what I can do about changing to a more off-the-shelf display.? A quick perusal of DigiKey doesn't turn up *any* 7- or 8-digit displays, and the 4-digit ones start at about twice the size (and twice the price, and I'd need two), but I'll keep looking.

In the meantime, if a smaller quantity would help out, I'm sure I can spare a few (or a few dozen, probably - I'll check my stock the next time i get to my warehouse). Contact me off-list and we can work out the details.
~~

Mark Moulding

Actually, I'm already using the MAX7219, because it does save so much work and there are easily-available libraries to drive it.? The reason I liked the display I'm using is that it's the right size (about 1-1/2" / 35mm wide), and has some separate indicator LEDs built in.? If they do run out, I'll just plant some smaller 4-digit displays directly on the board, along with some separate indicators.? This is all inside a chassis anyway, used for setup, configuration, and calibration, so it doesn't need to meet up with a fancy front panel.

One of the advantages of providing niche products is that they're not particularly sensitive to component pricing; most of the unit price goes to amortize the original engineering.? In most cases, there simply isn't a competitive product available, and other ways of accomplishing the customer's job are far more expensive, so everybody wins.

Thanks for the pointer to this display, though - having a couple of these around for quick knock-together projects could be pretty handy!
~~

Mark Moulding

Mark Moulding wrote:

Lee, I probably caused the availability problem with the original
display you were using. I found that to be a really neat display, so I
designed it into a specialized low-volume product I produce for a
client, and to ensure enough stock, I bought all they had (about 1,100
of them).

Hi Mark,

Aha! So THAT's where they all went! When we designed the badge, I ordered a couple hundred for the VCFMW show and follow-on orders. These were quickly gone; but when I tried to order more, MPJA said they were all sold. That was the "end" of the 6502 badges.

Luckily, I still had a couple boxes set aside for the Z80MC. Otherwise, I would have been out of business on it as well.

Then last year, one of the VCFMW guys (Mike Lee) found some more on ebay. So we were able to make another batch of badges for the show. I still have ~30 left, so the 6502 badges are currently available again. (Just don't buy 'em all).

Lee Hart

--
A designer knows he has achieved perfection not when there is
nothing left to add, but when there is nothing left to take away.
-- Antoine de Saint Exupery
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com

smmccown@... wrote:

Do you have a datasheet or part number for the replacement LED display?
I would like to read about it.

I bought them on ebay. No data sheet or manufacturer's name. It's marked 72R02PHIL, date code T9718.

Lee Hart
--
A designer knows he has achieved perfection not when there is
nothing left to add, but when there is nothing left to take away.
-- Antoine de Saint Exupery
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com

Richard Cini wrote:

The 9958 is a weird DIP packaging so maybe the 9918. The Retrobrew Computers N8 Home Computer uses it. Looks like the VDP, RAM, three buffer chips and some decoding.

Thanks Rich,

Designing video was "hard" back in the 70s/80s, so there were lots of specialized controller chips for people eager to get something out the door quickly. The Motorola 6845 was popular, but each IC manufacturer had their own. Intel had the 8275/76, RCA had the 1861, TI had the 9958 and 9918, etc.

They all work, but have also become rare and expensive today. I hesitate to design something with one, unless I have a bucket of them.

So, I'm inclined to follow in the footsteps of Woz, Sinclair, Lancaster, and other designers who used clever circuits to produce video with standard chips. I've attached two of my "brainstorms" in this path:

Z80-VID.PDF has 12 ICs, outputs 384x192 pixel NTSC/PAL video (enough for 24 lines of 64 characters), 128K RAM, PS2 keyboard interface, SPI, and a bit-banger serial port. It's an accessory board for the Z80MC, (kind of equuivalent to the Z80-SIO), and multiplexes the RAM between Z80 and video, so the Z80 does not stop while video is being output.

Z80-VIP.PDF has 11 ICs, outputs the same video, but is a complete free-standing "terminal". It has its own Z80, 32K RAM, 32K EPROM, UART serial port, and switch matrix keyboard. It uses the Z80's BUSRQ/BUSAK signals to stop the Z80 while video is being output (so the Z80 runs at about 25% speed). It's patterned after my 1802 VIP2K <>, and uses a simple state machine (counter/EPROM/latch) to create the video.

But both lack "elegance", and have too many parts to fit on an Altoids card. I could obviously use a bigger board; but keep "scheming" in case there's a way...

Lee Hart

--
A designer knows he has achieved perfection not when there is
nothing left to add, but when there is nothing left to take away.
-- Antoine de Saint Exupery
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com

Found this...



The 9958 is a weird DIP packaging so maybe the 9918. The Retrobrew Computers N8 Home Computer uses it. Looks like the VDP, RAM, three buffer chips and some decoding.

Rich

--
Rich Cini




?On 7/26/20, 2:44 PM, "Lee Hart" <[email protected] on behalf of leeahart@...> wrote:

Richard Cini wrote:
> Lee -- I know decidedly unvintage, but you can use an ATMEGA88 as a composite
> color video chip...

Of course I can. *Any* modern micro can generate video. For that matter,
there are many little boards I can buy that do it all for me. Nothing to
design, no software to write. But what's the fun in that? :-)

I guess it's like doing a jigsaw puzzle. You could just buy the finished
picture; no assembly required. But the fun is in the assembly.

And for me, the fun is in the design. Not the modern "beat every problem
to death with a sledgehammer" approach, but rather the Dr. Dobbs
"running light without overbyte" philosophy.

So, I set a hard goal for myself, and then see if I can achieve it. How
simple can it be and still do the job?

For inspiration, I look back on things like the Heathkit H19 terminal
(1979), Sinclair ZX80 (1980), and Voja Antonic's Galaksija computers
(1982). They all used a Z80 with minimal vintage hardware to produce a
terminal with keyboard and video. There are also Don Lancaster's "cheap
video" tricks, which mostly centered on the 6502.

I have several designs that *almost* fit on an Altoids size card. But
none have quite given me that "aha" moment yet.

Lee Hart
--
"We do these things not because they are easy; but because they are
hard." -- President Jack Kennedy, on the Apollo moon mission
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com

Hi Lee,

Do you have a datasheet or part number for the replacement LED display?? I would like to read about it.

Thanks, Steve

Lee, I probably caused the availability problem with the original display you were using.? I found that to be a really neat display, so I designed it into a specialized low-volume product I produce for a client, and to ensure enough stock, I bought all they had (about 1,100 of them).? I figure that once that supply is exhausted, the product will have made enough profit to justify re-spinning the board for a new display.? I did the same with the user-interface buttons I'm using, too.

This may not seem like a particularly sound practice for a real commercial product, but it's worked out well for me; if I guess right about the projected quantity, it can save quite a lot of money.? There's certainly plenty of precedent: Many of the 70s- and 80s-era home computer kits used this model, as did (and still do) many of the "boutique" audio and musical instrument manufacturers.
~~

Mark Moulding

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Richard Cini wrote:

Lee -- I know decidedly unvintage, but you can use an ATMEGA88 as a composite
color video chip...

Of course I can. *Any* modern micro can generate video. For that matter, there are many little boards I can buy that do it all for me. Nothing to design, no software to write. But what's the fun in that? :-)

I guess it's like doing a jigsaw puzzle. You could just buy the finished picture; no assembly required. But the fun is in the assembly.

And for me, the fun is in the design. Not the modern "beat every problem to death with a sledgehammer" approach, but rather the Dr. Dobbs "running light without overbyte" philosophy.

So, I set a hard goal for myself, and then see if I can achieve it. How simple can it be and still do the job?

For inspiration, I look back on things like the Heathkit H19 terminal (1979), Sinclair ZX80 (1980), and Voja Antonic's Galaksija computers (1982). They all used a Z80 with minimal vintage hardware to produce a terminal with keyboard and video. There are also Don Lancaster's "cheap video" tricks, which mostly centered on the 6502.

I have several designs that *almost* fit on an Altoids size card. But none have quite given me that "aha" moment yet.

Lee Hart
--
"We do these things not because they are easy; but because they are hard." -- President Jack Kennedy, on the Apollo moon mission
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com

Lee --

I know decidedly unvintage, but you can use an ATMEGA88 as a composite color video chip. I use it on my 6502 SBC. It needs an oscillator (16MHz), two resistors, the chip and an RCA jack (or flying leads to an RCA jack). There are VGA solutions too, using for example the Propeller chip. Take a look at the board from S100Computers. Obviously you can cut a lot out of the design (like decoding and port selection, the LED displays, etc.).





Rich

--
Rich Cini




?On 7/26/20, 1:31 PM, "Lee Hart" <[email protected] on behalf of leeahart@...> wrote:

ajparent1/kb1gmx wrote:
> Thump thump.. testing 123 test test...
> IS there any life or is it dead?

Hi Allison,

It's alive; just sleepy. Too many distractions, I guess. Let me see...
what have I been doing with the Z80MC lately?

1. The 7-digit LED display has become hard to get. I found a
replacement, with green 7-segment LEDs. It's also a surplus part, but I
got enough to last a while; so I can keep producing kits for the
forseeable future. Physically, it has wire leads instead of pins (they
have to be bent slightly to fit the holes in the PCB) and lacks the
"steps" in the corners of the old red LED display. That's it in the
picture of the Front Panel card on my web page
<>.

2. I changed the LED-photoresisor optocoupler (used to control the piezo
speaker) to a standard LED-phototransistor part. It added a resistor
(and I always fight to minimize parts), but it's a standard part and so
easier to get.

3. I made a few improvements to the CPU board:

- I flipped the 5v regulator upside down, so its metal tab faces
*away* from the PCB; this provides better cooling.

- It also made room to add a 6-pin power/serial header (same as on the
Front Panel card). Use this header with a USB-serial cable run the CPU
board "barefoot" (without any other cards). The plan is to sell the CPU
board by itself for half the price, for any little Z-duino projects you
may have.

- I added jumper options to put BUSAK and BUSRQ on the bus in case
they're needed. but there's an error in the silkscreen; the HALT and
BUSAK are swapped. I'll fit it in the next batch of PCBs.

4. I've been "scheming" for a way to add a video/keyboard "terminal"
card. I have several designs, none of which I'm entirely happy with. We
can discuss them if anyone's interested.

5. A customer found a bug in the Dunfield BASIC; it can crash when
handling strings. I haven't had time to track this one down yet. Anybody?

What have YOU been doing with the Z80MC?

Lee Hart

--
If happiness is on your mind, here's a daily list to find:
- something to do
- something to look forward to
- someone to love
- someone to take good care of
- and misbehave, just a little
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com

ajparent1/kb1gmx wrote:

Thump thump.. testing 123 test test...
IS there any life or is it dead?

Hi Allison,

It's alive; just sleepy. Too many distractions, I guess. Let me see... what have I been doing with the Z80MC lately?

1. The 7-digit LED display has become hard to get. I found a replacement, with green 7-segment LEDs. It's also a surplus part, but I got enough to last a while; so I can keep producing kits for the forseeable future. Physically, it has wire leads instead of pins (they have to be bent slightly to fit the holes in the PCB) and lacks the "steps" in the corners of the old red LED display. That's it in the picture of the Front Panel card on my web page <>.

2. I changed the LED-photoresisor optocoupler (used to control the piezo speaker) to a standard LED-phototransistor part. It added a resistor (and I always fight to minimize parts), but it's a standard part and so easier to get.

3. I made a few improvements to the CPU board:

- I flipped the 5v regulator upside down, so its metal tab faces *away* from the PCB; this provides better cooling.

- It also made room to add a 6-pin power/serial header (same as on the Front Panel card). Use this header with a USB-serial cable run the CPU board "barefoot" (without any other cards). The plan is to sell the CPU board by itself for half the price, for any little Z-duino projects you may have.

- I added jumper options to put BUSAK and BUSRQ on the bus in case they're needed. but there's an error in the silkscreen; the HALT and BUSAK are swapped. I'll fit it in the next batch of PCBs.

4. I've been "scheming" for a way to add a video/keyboard "terminal" card. I have several designs, none of which I'm entirely happy with. We can discuss them if anyone's interested.

5. A customer found a bug in the Dunfield BASIC; it can crash when handling strings. I haven't had time to track this one down yet. Anybody?

What have YOU been doing with the Z80MC?

Lee Hart

--
If happiness is on your mind, here's a daily list to find:
- something to do
- something to look forward to
- someone to love
- someone to take good care of
- and misbehave, just a little
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com

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