Is anyone interested with the Z80?

Did you know that the Z80 has different memory access timings for instruction fetches and standard memory accesses?

I worked at Mostek maintaining the Fairchild Sentry testers used to test the Z80s when they first began to manufacturer them. The second computer I every

built (parts, pcb, solder) was the SDB-80 which was the Mostek Software Development Board for the Z80 with 16K bytes (8 - MK4116 16K bit) dynamic RAMs

which Mostek also made. The first wire wrap board I ever made was a 48K byte dynamic RAM board also using MK4116s that worked with the SDB-80. I can

tell you there were a bunch of happy technicians when we were told that Mostek would be second sourcing the Z-80 and even happier when we were told we

could buy SDB-80 kits and build them ourselves! Those were really fun days. I still have a Zilog Z80 in a ceramic package that says it was manufactured in

Dallas even though Mostek was actually in Carrollton a suburb in Dallas County just north of north-west Dallas.

I worked at Mostek maintaining the Fairchild Sentry testers used to test the Z80s when they first began to manufacturer them. The second computer I every

built (parts, pcb, solder) was the SDB-80 which was the Mostek Software Development Board for the Z80 with 16K bytes (8 - MK4116 16K bit) dynamic RAMs

which Mostek also made. The first wire wrap board I ever made was a 48K byte dynamic RAM board also using MK4116s that worked with the SDB-80. I can

tell you there were a bunch of happy technicians when we were told that Mostek would be second sourcing the Z-80 and even happier when we were told we

could buy SDB-80 kits and build them ourselves! Those were really fun days. I still have a Zilog Z80 in a ceramic package that says it was manufactured in

Dallas even though Mostek was actually in Carrollton a suburb in Dallas County just north of north-west Dallas.

Are you still in the Dallas area. So am I.

Clem

Wow! that's amazing that you got such a large DRAM board working with Wire-wrap.

Do you still have any photos or schematics of it?

It was quite rare to come across Mostek parts in Australia. We usually got Zilog, SGS and Sharp.

And from memory the SGS parts didn't support the undocumented instructions.

Yep, lived here all my life (more years than I want to admit to).

No photos but the schematics were from a Mostek Z80 application note which I may still have. I used a tool from Vector called the Slit and Wrap which used

small spool of wire coated with a soft insulator kind of like magnet wire that was slit by the wrap bit just before it was wrapped on the post. It was a great tool

for speeding up wire wrapping with one fatal flaw. If two wires pressed against each other hard enough, they could displace the soft insulator and short.

When ever I powered it up and it did not work I would have to look for two wires pressed against each other in a rats nest of wires (actually I was more

systematic than that but there were always problem areas) and separate them. When the offending wires were separated it would usually make a distinctive

"plink" sound so I knew when I found it.

I used the same tool and a Z80 to wrap up a 256 x 240 x 4 bit/pixel graphics display controller. The schematic was from Byte Magazine and I modified it from

the original 1 bit/pixel configuration and to use static RAMs that were fast enough to allow the Z80 full speed access to the video RAM by interleaving the

accesses with video timing generator. The Z80 assembly language software had to be entered in by hand to be assembled and of course modified to handle

the multi-bit/pixel mod and to use a 8 bit parallel interface to the SDB-80. I believe it only had commands for pixel read/write, line and circle drawing.

Unfortunately after quite a few sessions of find the Slit and Wrap short I gave up and disassembled it for the parts and never used my Slit and Wrap again.

Like I said, fun (and sometimes frustrating) days.

Ahhh!

The days of triple power supplies (+5, +12 and -12V).

Slit-N-Wrap from Vector.

It's still available today but not on the e14 catalogue.

I used a competing product called JUST WRAP and I think I've still got the blighter!

Yes, three voltage power supplies ruled then. And you can add +24V for the 8" floppy drives but they were usually in their own case with a separate

+5V, +24V power supply. The MK4116, and all other dynamic RAMs of the time used +5V, +12V, -5V which was usually derived from the -12V which

came in handy for  RS-232RS-232 drivers

I thought it was Slit-N-Wrap but I couldn't remember so I went for the long version. I thought Vector was still around, I wonder if they fixed the shorting

problem ?

I remember the Just Wrap too and I know I was very interested but for some reason, lost in the mists of time, I never bought one which is made even

more curious after all the Slit-N Wrap problems. I think I just went to pre-cut wire wrap wire (which I still cut to length) with an electric wire wrap tool but ...

I still have a motorized Slit-N-Wrap and I still use it once in a while. It used to be really fast for wiring low-speed backplanes - much faster than manually soldering connectors on PCBs. I built a circuit that would make it automatically stop wrapping after 7 turns.

I never had problems with shorts. They have 2 types of wire, one with a Tefzel (Teflon) jacket that is thicker than normal Kynar, the other is  a thin green enamel coating (a bit like magnet wire). I never had problems with either type although I was always careful not to let the green stuff rub on square pins.

The Slit-N-Wrap wire is 28AWG and normally 30AWG is used for Wire Wrapping.

I usually use 24, 26 and 28AWG for prototyping because I find that 30AWG is a bit too flimsy.

Dobs of glue are also useful for holding wires in place.

COMPACT  wrote:

 

It was quite rare to come across Mostek parts in Australia. We usually got Zilog, SGS and Sharp.

And from memory the SGS parts didn't support the undocumented instructions.

The latest post in this thread was recent enough for me to dare 'reply' to this 2016 entry - hope that's OK with you ?

During the '80s I've been professionally involved in a number of commercial projects, built around the PC-1500A pocket computer from Sharp.

This was often referred to then as a 'BASIC programmable calculator', though its functionality, capabilities, and the actual applications surpassed

that status by far.

With only superficial knowledge of microprocessors, I've always wondered about Sharp's own LH-58xx family. As far as I know, it has only been

utilized in the PC-1500 and its successor, the PC-1600. It wasn't until recently that I learned that Sharp had (and still has) its own line of OEM

4 and 8 bit microprocessors. The LH-5080 e.g. is offered as a member of the Sharp  Z80 family, LH-0080.

For me this raises several questions:

- Is the LH-5801 really a Z80 derivative, as most sources over time have stated ? Doesn't the model number, 5800, seem odd, even peculiar,

   when one realizes the importance of the Motorola 6800 in those days ?! In other words: LH-0080 makes sense, better still: is clear - LH-5800

   is confusing. The only explanation I could think of, would be, Sharp meaning to discern her OEM products from her microprocessors intended

   only for use in her own apparati - i.c. her line of pocket computers. Btw Sharp herself makes no mention of the Z80 (nor any other microprocessor

   for that matter) in her Technical Reference Manual. (http://www.pc-1500.info/Data/Service_Manuals/PC-1500_Technical_Reference_Manual.pdf )

- Anybody has a clue as to what the letters, LH, stand for, and what the 5 might refer to ?

  (Sharp being proud of her early chip design and production capabilities, called one of her seventies calculator lines: Elsi Mate, where Elsi stands

   for ELSI - Extra Large Scale Integration)

- The CMOS LH-5801 had an impressive number of on-chip facilities/peripherals - probably more than the (standard ?) Z80.

   I have not been able to find a (useful*) comparison with the Z80 itself, derivatives, or other microprocessors from the same era. Anybody ?

    *(cpu-world hasn't brought me any further).

Thanks or answering !

Ray

Hi Ray,

I've not looked at Z80 for an extremely long time, so I could be wrong, but looking at this PC1500 machine code article (PDF) the instructions do not look like Z80.

For instance, on the last page of the PDF, there is this example program:

Taking an example, the red instruction, the Z80 does not have an RTS instruction according to here: Z80 / R800 instruction set

There's a RET instruction for the Z80, but it has a different opcode too (0xC9, not 0x9A).

Also, according to here: Frank C. Odds : Probe! a disassembler for the Sharp PC-1500 - PC-1500.info

the PC-1500's CPU only has three registers.

So, I believe that while it may have similarities to CPUs such as the Z80 or indeed any other CPU from the time, it's not a Z80 derivative (or not a very close one), nor compatible with z80 at mnemonic or opcode level.