Paul Bigwood wrote:

Lee,
I was very interested in the G Barrow 8080 S100 board octal display
and keypad. A Google search turned up the user manual with cct and
rom code.

Do you mean George Morrow's "Keyed-Up" combination front panel and 8080 CPU board? This one? <>

joshbensadon via Groups.Io wrote:

There is barely enough space for the LED's they're packed in there like
commuters on the 5 O'clock train!
But, you can very easily alternate colours of LED's. I'm using Red and
Yellow, in sets of 4 for HEX.
Nothing stopping you from doing sets of 2,3,3. Might need to count out
the right number of LED's for both layouts.

That's a good idea. :-) The LEDs are evenly spaced, so color could be used to separate them into hex or octal formats. It should be easy to supply enough LEDs so the builder can choose which he wants.

The serial monitor is a little harder. Right now, it's written for hex. But the source is available, so you could change it for octal.

Is it planned to add a SD card for cp/m?

The Z80MC already has it. If you mean the 8080 "Altaid 8800", it doesn't have an SD-card... or for that matter, *any* modern parts. I was aiming for a pure retro-design.

It does have jumper options for bigger modern "bytewide" RAMs and ROMs. In 1976 (the ficticious introduction date), the only options would have been a 2716 2K EPROM and 2K RAM (and they were both very new and expensive).

But as Intel's Gordon Noyce observed, memory chip size doubled every 2 years!

--
ICEs have the same problem as lightbulbs. Why innovate and make
better ones when the current ones burn out often enough to keep
you in business? -- Hunter Cressall
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com

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ajparent1/kb1gmx wrote:

With 8080 RST7 is free (bus to 1s using pullups)

Yep! That's how I did it on the Altaid 8800 (an 8080 version of Membership Card) <>. But that has to change to make stock versions of DDT (or SID or ZSID) work.

For the Z80MC, DRI application note #07 is the patch to change DDT to use RST6 instead of RST7. We made the patch, and put a copy of DDT with it (named DDT-V6.COM) on the DISK-1 image for the SD-CARD.

Josh has also updated his Windows CP/M Explorer program to version 1.3.

Both have been uploaded to the website <>

DDT is a very compact program as well.

It certain is! There are some very clever tricks to keep it small. Whoever the programmer was (Gary Kildall himself?), he certainly knew how to code for limited resources.

heath H8 the front panel was a source of issue for later software. It
was its weakness in the works of Altair and IMSAI.

It depends on what you want. Front panels are expensive and hard to use; after the initial novelty wears off, they don't get used much.

The Heath H8 keypad and 7-seg LED monitor was a lot easier to use; and cheaper, too. It remained useful on a regular basis. For one thing, it would continuously display the last register, memory address, or I/O port even while your main program ran. But as you say, it depended on an interrupt, and for the CPU to be running the monitor program. It took away a little execution time (but you could turn it off to make your programs run a little faster).

One of the cleverest early Front Panels was George Morrow's "Keyed-Up". It was an 8080 CPU board for the S-100 bus that included a keypad and 7-seg display. It ran software to work; but that software was a tiny 32-byte PROM. Instead of depending on an interrupt, it opened the 8080 data bus, and inserted its PROM. The card had a separate program counter for the PROM; it didn't depend on the CPU's PC. So his little program ran no matter where the CPU was, to let you examine and change memory, etc.

Lee

--
There is a computer disease that anybody who works with computers knows
about. It's very serious, and interferes completely with your work. The
trouble with computers is that you 'play' with them! (Richard Feynman)
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com

With 8080 RST7 is free (bus to 1s using pullups) if you want any other you need to assert that on the bus
an octal bus driver with the inputs set to RST3 or 4 is suggested.? RST6 is also in a sorta sometimes
used space as well.?

DDT is a very compact program as well.

heath H8 the front panel was a source of issue for later software.? It was its weakness in the works
of Altair and IMSAI .? Both of them the lights for address were just buffers address the Data leds?
were also same and the processor wait stated between operations.

Most of the "smart" front panels the address leds were again off the address bus
but the data was a latched port? both input and output and the very small usually 256 bytes?
program interrogated switches or loaded the latch. Most all avoided interrupts as they were
difficult (who knows what CPU) and often got in the way.? When running the leds show data
and address off the bus and the FP know if it was running or suspended.

the 8080 FPs often used tricks like 1802 DMA load mode save for it was done via wait and?
jamming nop or jumps for a single cycle.

Allison

ajparent1/kb1gmx wrote:

Having a [Front Panel] should be seamless, least it was on my old
Altair when it behaved. There is no reason why CP/M should not run
with a FP. Also the blinkin lights thing.

Yes; the blinkin-lights are an important feature of a FP. "What are all those blinking lights doing, son?" "Impressing you, dad!"

A hardware front panel shouldn't have any effect on the computer. But a software-driven front panel (like the Z80MC or a Heath H8) has to interact. It needs a program in memory to run it, and an interrupt to periodically update the blinkin-lights. The interrupt routine requires time, and that there be a working stack, among other things.

The Z80MC uses RST7 for its timer/serial/front panel interrupt. We just discovered that CP/M's DDT also uses RST7 for breakpoints. Thus they conflict; so DDT will crash the system!

There are a couple ways to fix this:

1. Software: I've been looking at the DDT source, and there is an option to use RST6 instead of RST7. DRI apnote #7 (attached) describes the procedure for patching DDT to use RST6. It says to change address 01EB from FF to F7.

But, Bob Kircher reports that his copy of DDT had the FF at 01EC (not 01EB). So he patched to 01EC from FF to F7; and it worked. :-)

2. Hardware: It is also possible to move the hardware interrupt from RST7 to some other interrupt. But this requires some cuts-n-patches, plus some software changes to the ROM and BIOS to account for it. So I think we'll save that for a future revision.

DDT loads to 100H then senses the base of BDOS and relocated
to under that so the space from 100h to below DDT is available for
user programs that would nominally be at loaded at 100H when
finished or debugged.

Yes; DDT is a *very* clever program! The source has been published ro all to see. Besides relocating itself, it can also allow the program it is debugging to overlay parts of it, and still keep the remaining parts working.

Lee
--
There is a computer disease that anybody who works with computers knows
about. It's very serious, and interferes completely with your work. The
trouble with computers is that you 'play' with them! (Richard Feynman)
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com

Yes, having A FP should be seamless, least it was on my old Altair
when it behaved.? There is no reason why CP/M should not run
with a FP.? Also the blinkin lights thing.

The Xmodem bug,? That may be a feature. ;)? Modem program in
the CP/M space were always troublesome as some wanted a well
configured IO byte, others did direct IO and had to be tweaked for
the IO device in use (SIO-A or B, 8251, 6850, 2651, 16450,
SIO/(drt or SIO2)? and many others often different enough.

DDT the likely clash is RST7 (address 38) as DDT uses that as a
debug return point.? ?Usually front panels had port FFh as an input
from the FP switches (sense, often used by non cpm for setting up
what IO exists).? Also FFH is the opcode for RST7 so missing memory
(altar/imsai) has pull-ups so by default no ram, is a RST7.

FYI the most nasty bug on the Altair was noise on all the front panel
wires to the bus causing the appearance of "flying bits" and crashes.?

DDT loads to 100H then senses the base of BDOS and relocated
to under that so the space from 100h to below DDT is available for?
user programs that would nominally be at loaded at 100H when
finished or debugged.

Easier would be the smaller T-11 as its a more conventional 40pin.

Allison

Paul Bigwood wrote:

Hi Lee, Love it [Altaid 8800]. Do you have prices and availability of a kit yet?

TBD (To Be Detirmined). But hopefully by the end of the year. :-) Price will be similar to my other little computers (1802 and Z80).

Lee80 Hart

--
There is a computer disease that anybody who works with computers knows
about. It's very serious, and interferes completely with your work. The
trouble with computers is that you 'play' with them! (Richard Feynman)
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com

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I recently updated the Z80 Membership Card CPU card to rev.B, and the Front Panel card to rev.D. No big changes; but here are the improvements:

CPU rev.B

The 5v regulator U8 has been flipped upside down, so its metal tab faces up (away from the board) instead of down (against the board). This improves its ability to dissipate heat if you're running with an unregulated 6-9vdc supply.

I added a 6-pin power/serial connector P4. Its pinouts are the same as P4 on on the Front Panel, so a Sparkfun 5v USB-serial cable #9718 plugs right in. This connector is located in the same place as U8; so install one or the other (not both). If you are getting 5v power from the USB-serial cable, then you don't need the U8 regulator.

P3 was added to jumper the serial input to the Z80 /INT input. This connection was made on the Front Panel; but with the P3 jumper, you can use the CPU board all by itself (no front panel). Use a serial terminal to talk to the monitor or run BASIC or other programs.

Options were added to jumper bus P2 pin 28 to HALT or /BUSAK, and bus P2 pin 29 to /NMI or BUSRQ. This provides access to these pins if needed for your own accessory cards.

Front Panel rev.D

I replaced the hard-to-find LED-photoresistor coupler with a standard LED-phototransistor coupler. This required a new pulllup resistor, R2D.

The optocouplers I bought seem to have a little too much gain. Some users have found that they can still hear the piezo when it should be off. My hearing isn't good enought to tell! If you hear it, try a lower value pullup for R2D, or replace the optocoupler with a lower-gain part.

Forward into the past,
Lee Hart

--
There is a computer disease that anybody who works with computers knows
about. It's very serious, and interferes completely with your work. The
trouble with computers is that you 'play' with them! (Richard Feynman)
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com

timgreenowb via Groups.Io wrote:

Just joking. I forgot to put a smiley ? on my post. It's the chip
from a DEC PDP-11 and obviously wouldn't fit in a tin.

Well, there are PDP-8 and PDP-11 clone kits (google PiDP-8 or PiDP-11). They use a Raspberry Pi as their "brain", which would fit in an Altoids tin.

Almost *everything* has been put in an Altoid tin.

I had a mad idea to put one of those tiny 12vdc-to-120vac inverters that plug into an auto accessory (cigarette lighter) socket in an Altoids tin, along with 12v worth of rechargeable batteries and a small PV panel. When the sun shines on it, you have a "nuclear power plant" in an Altoids tin. :-)

Lee Hart

--
There is a computer disease that anybody who works with computers knows
about. It's very serious, and interferes completely with your work. The
trouble with computers is that you 'play' with them! (Richard Feynman)
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com

Just joking.? I forgot to put a smiley ? on my post.? It's the chip from a DEC PDP-11 and obviously wouldn't fit in a tin.? I got the idea from here:



Tim

timgreenowb via Groups.Io wrote:

Maybe Lee could do a J11 Membership Card next.

I'm too "vintage", I guess. What's a J11? What do these two giant chips do?

Josh and I have currently been working in the opposite direction. We've put an Altair 8800 in an Altoids tin. We call it the "Altaid 8800". :-)

<>

Lee80 Hart
--
There is a computer disease that anybody who works with computers knows
about. It's very serious, and interferes completely with your work. The
trouble with computers is that you 'play' with them! (Richard Feynman)
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com

Maybe Lee could do a J11 Membership Card next.

From: bill rowe <bill_rowe_ottawa@...>

Sent: Oct 21, 2019 7:34 AM
To: [email protected]
Subject: [Z8MC] Z80 Not Z8

Hi Charles. This group is centered around the Z80 Membership Card. The Z8MC was just my clumsy abbreviation. I was not aware that there was such a thing as a Z8 till yesterday. I don’t know anything about compatibility.

in a few days I’ll rename the group to Z80MC unless someone has a better idea. That will change the email address so I’m going to wait until membership settles down.

sorry for the confusion.

Hi Charles and Bill,

Yes, the Z8 is a different (later) Zilog microcomputer. The Z8 was built for smaller controller applications, similar to the Intel 8048-51 family. It has built-in RAM and ROM, and some on-chip I/O. The instruction set is completely different.

I agree on changing the name of the group from Z8MC to Z80MC. Less confusing!

Lee Hart

--
Excellence does not require perfection. -- Henry James
--
Lee A. Hart

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Hi Charles. This group is centered around the Z80 Membership Card. The Z8MC was just my clumsy abbreviation. I was not aware that there was such a thing as a Z8 till yesterday. I don’t know anything about compatibility.

in a few days I’ll rename the group to Z80MC unless someone has a better idea. That will change the email address so I’m going to wait until membership settles down.

sorry for the confusion.