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.

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.

You can create your own blog on any topic just by clicking on the "Create" button at the top of the page.

Threads like this Z80 topic just fade from view unless members keep adding anecdotes, so I think it is great to add stories directly to the thread, even if they are only peripherally related.

As a newbie to this forum, I'm afraid I don't quite understand.

I don't have my own blog, and was responding to an 'invitation' by COMPACT.

You could put a link here to your own blog, or put the story here. I can't speak for everyone but either would be fine with me.

Hi COMPACT,

May I add another PC-1500A project story in response to your earlier interest, and present that, assuming you have also read my posts to Shabaz ?

(It would be boring i.m.o. to tell intertwined stories to two forum members, as if they didn't read each others 'incoming' posts, wouldn't it ?)

This story unfolded in the aftermath of PC-1500A's demise - ending in the permafrost of Siberia ...

As the story hasn't anything to do per se with Z80, does it interest you, and would it be acceptable in this thread ?

Would appreciate hearing from you

Cheers

Ray

Hi Shabaz,

As Appendices at the end of the 276 page PC-1600 Tech Ref Manual I found mnemonics, op-codes, and what have you of both the SC- and the

LH-processor. Not my cup of thea, really ... But maybe someone else finds the clues, required to answer the question: was LH-5801/3 a Z80

derivative, or not ?

For me Chapter 7 is much more evocative, and it confirms my belief all along, that not only 'Ol Blue Eyes did everything "My Way" ...

It is quite impressive what Sharp has integrated on-chip*, next to the processor 'core' - this goes for the Z80A derivative, as well as for the LH.

I've called what they have packed into this pocketcomputer "no mean feat". If you look at the features, you can say that again:

- 3 microprocessors, two 8-bit main CPUs (one emulating the PC-1500A a.o.) + one 4-bit subprocessor (I/O)

- 3 x 36 kB ROM

- RS-232C I/F

- serial optical I/F, 38.4 kbaud

- analog input (ADC)

- automatic power off with external wake-up from peripheral

- floppy and RAM-disk options

- 60-pin fully programmable system/expansion bus output

- 2 memory module slots

Impressive ? Sure ! A joy to work with (as a programmer or a user) ? Not really ... And that's a shame.

PC-1600 has never been able to replace PC-1500A in the market, possibly because it became the victim of its own over-complexity ?

At the time (mid eighties and on) Sharp had already her organizer concept ready, later shared in the PDA concept with Apple (Newton),

and so probably didn't care too much ... (PC-12xx, 14xx, E200, and E500 series thriving)

Cheers

Ray

* a.o. the complete port processor, LH-5811, of PC-1500 in the SC main CPU

Hi Ray,

It could be derived from the Z80, I really cannot tell one way or another.

I used the Z80 a lot in the home 8-bit computer era with plenty of machine code (I had no assembler) but I cannot recall much apart from a few instructions and op-codes that won't seem to leave the brain : )

The embedded 8-bit stuff I encountered later was mostly Motorola based (6805 and 6811 particularly) and a few other manufacturers.

Hi Shabaz,

Further to the Z80 discussion in relation to the Sharp PC-1600: reading the Technical Reference Manual, answers to several questions can be

found:  http://pockemul.com/Documents/PC1600/PC1600TechnicalReference.pdf .

First of all, the main CPU, SC-7852, is a Z80A-clone. Second: Sharp specifies LH-5801/3 for what they call the subprocessor; so early production

probably was equipped with the 'old' PC-1500A CPU, which was then later on replaced by an upgraded version, the LH-5803.

After that the LH-58xx series was obviously discontinued, in favour of their SC family of micrprocessors - maybe to improve Z80(A)-compatibility.

The best - most comprehensive yet concise - overview: https://sharppocketcomputers.com/index.htm#basic . As an aside: It is remarkable that

after the 4-bit SC dual processor in Sharp's first pocketcomputer, the PC-121x had been succeeded by the 8-bit LHs, 4-bit SC-processors were

used again in later models.

Where the master-slave operation in the PC-1211 worked flawlessly, cooperation between the SC-Z80A and the LH-subprocessor more often than

not led to system instability, up to complete crashes.

The main disappointment with the PC-1600 however was its substandard (for Sharp at least !) LCD. Cramming this 4 times bigger display plus an

extra full size PCB, etc. into the same case as the PC-1500 however, is of course no mean feat ...

Maybe taking a glance at mnemonics and opcodes in the PC-1600 Tech Ref Manual can bring our decission nearer as to the LH-5801 was a Z80

derivative, or not. Memory allocation of the SC-Z80 surely differs considerably from that of the LH-5801, yet addressing range is equal (512 kB),

thanks to the flipflop registers in the LH; the SC seems having to do a lot of bank switching in large applications ...

Cheers

Ray

Hi Shabaz,

Very interesting musings about Z80 and possible 'mimicry' ... And thank you for the literature suggestions.

I believe having gotten some idea of Sharp policy in the dozen or so years I've made a living out of their products in many applications.

Do share your viewpoint that a lot of Japanese manufacturers of the time had more than enough innovation capability of their own, in order

not having to rely on copying; they did however clever- and selectively enter into strategic alliances and joint ventures.

I was appalled to learn that the company was recently taken over by Foxconn, of all the lousy manufacturers of today ...

The Japanese goverment should be ashamed for not having done anything to prevent this - the company that produced the unique amber

EL-displays for the Space Shuttle and where Philips had to buy all their LCD patents !

Back to the good ol' eighties and Sharp policy: I still feel the only explanation that makes sense for the model number, (LH-)5801, is as follows.

Next to their OEM production of Z80 clones - LH080, etc. - they wanted a proprietary microprocessor design for their indeed innovative line of

pocket computers. However they did not want to isolate these products too much from the brands and models that had become well-known

market leaders, in order to reach the broadest possible acceptance. So they devised the number 5800, with a wink to the 6800; but in order

to prevent the impression that they would suggest to make a predecessor, or down-graded version, they made the number their own by changing

it into 5801. Speculative ? Sure, but have I "entered into the realms of phantasy" ?

There was btw a LH-5803, which was meant to emulate the 1500 in its successor, the PC-1600 in order to attain full SW-compatibility. (It didn't

work 100% - much like my XP Pro overlay on Windows 10; this was probably also the reason for the PC-1600 being a less stable system than the trustworthy 1500).

Cheers

Ray

Hi COMPACT,

Sorry for my late response.

Thanks for your friendly reply, and for sharing your broad knowledge to fill-in some of the white spots in mine.

Further to the Nestlé project (and risking being thrown out by the moderator on account of wandering too much off topic ...): the 'poor'

PC-1500A had to communicate with 68000 processors in the Swiss units. When the info required to tackel this problem didn't come in time

to meet the project deadline, I decided to try and overcome the speed differences ... in BASIC (call me crazy). The only solution to get around

a formal handshake was applying probability calculation. It worked fine and reliable.

Reading the history of the Z80, it seems safe tot conclude that Sharp must have been (one of) the very first (1980/81) to produce a CMOS

derivative (?) with many on-chip extras. Just out of curiosity I've once tested the PC-1500A for power consumption (keep in mind that there

was also an I/O controller on board, the LH-5811). Battery life was specified as 300 hrs, i.e. with the usual unrealistic operational limitations.

So after a fortnight of continously running an endlessly repeated program with heavy duty calculations, that made as much use as possible

of display functions, and most of all of the BEEP option, I expected to find my PC-1500A 'dying'. But after more than 3 weeks only the LCD

contrast showed some signs of a nearing 'low battery' condition. Unfortunately I had to abort the experiment, simply because I needed the

pocket computer for my programming work.

The first assembler, as far as I know, was made by Rasso von Schlichtegroll, fairly soon after the PC-1500's introduction; later he developped

a successful line of system programs and tools under the RvS brand, eventually commercialized by the Holtkötter publishing firm.

Jumping to the present, recently produced emulators may be the best way to keep the PC-1500(A) alive (and leave curious young users

in awe). As to the limited storing capacity of RAM chips in those days: the LH-5811 has a direct adressing capability of 64 kB - nothing fancy;

but because of the PU and PV flipflop registers, the full addressing range was 512 kB. And would you believe it: in the early eighties a small

third party company, AMS in Germany on the Danish border, managed to pack this huge amount of storage inside the pocket computer !

I'm not sure if/how his maybe conflicted with an eventual RAM module in the bay for external memory ... Later they had their Gold Card

produced in Taiwan for the top models in Sharp's organizer line: 256 kB, while Sharp was still fiddling with 32/64 kB.

Didn't know the TI-84 was Z80-based; always wanted to have one, never got around to it ... The origin of my interest stems from the late

seventies, and was thus calculator-oriented. I could go now into the old AOS vs. RPN debate, but this would be a) off-topic, and b) maybe

not of interest to anybody in this group. Suffice it to say that It is useless to try and grasp Sharp's design concept for its pocket computers

without taking her EL-5100 scientific calculator into account.

Cheers

Ray

Hi Ray,

At around that time, a lot of the handheld devices were getting powerful, so the ultimate decision to use that instead of any other device may have been simply because it was what someone was experienced in.

From the very little production/shop floor experience I have, it was interesting (at the places I worked) to see that the tools used in production were different to what the rest of the organisation were using. In other words, different CAD tools, different procedures, and different hardware. I'm not saying it is ropey, but a lot of stuff is designed to be one-off or very low quantity production.

Regarding the suggestion of Z80 origins made to look like a non-Z80 device, I've no idea. Certainly it won't execute Z80 software without modification and assembly with a different assembler.

Many processors at the time were similar, from a birds-eye view. Even the different processor designs that soon emerged like RISC and SPARC still have instruction sets and registers, and buses.

There was historically plenty of anti-Japanese tech sentiment in the 1980's, when many people thought that Japanese firms were copying or stealing ideas. That idea still exists today. It's unfounded, and likely no more than western firms stealing western ideas from each other. Perhaps that sentiment inspired the suggestion that it looks similar to the Z80 I cannot tell, since I don't know where and when that suggestion originated. The Japanese government encouraged firms to buy rights to patented tech, that was a major policy at the time.

Depending how keen you are to research down that road, there are some books worth reading, they mention names of people who would know better than speculation, of which unfortunately there is a lot of on the Internet. The first is We Were Burning, and the second is Industrial Innovation in Japan. The first is an easier book to read. According to that, Sharp was extremely quick off the block developing calculators, and amongst the first to productize (not invent) CMOS, so it's quite natural they would either license a Z80 design, or design their own chip. Neither of which would be good reasons to fake instruction names to look like a different processor.

Hi Ray,

At around that time, a lot of the handheld devices were getting powerful, so the ultimate decision to use that instead of any other device may have been simply because it was what someone was experienced in.

From the very little production/shop floor experience I have, it was interesting (at the places I worked) to see that the tools used in production were different to what the rest of the organisation were using. In other words, different CAD tools, different procedures, and different hardware. I'm not saying it is ropey, but a lot of stuff is designed to be one-off or very low quantity production.

Regarding the suggestion of Z80 origins made to look like a non-Z80 device, I've no idea. Certainly it won't execute Z80 software without modification and assembly with a different assembler.

Many processors at the time were similar, from a birds-eye view. Even the different processor designs that soon emerged like RISC and SPARC still have instruction sets and registers, and buses.

There was historically plenty of anti-Japanese tech sentiment in the 1980's, when many people thought that Japanese firms were copying or stealing ideas. That idea still exists today. It's unfounded, and likely no more than western firms stealing western ideas from each other. Perhaps that sentiment inspired the suggestion that it looks similar to the Z80 I cannot tell, since I don't know where and when that suggestion originated. The Japanese government encouraged firms to buy rights to patented tech, that was a major policy at the time.

Depending how keen you are to research down that road, there are some books worth reading, they mention names of people who would know better than speculation, of which unfortunately there is a lot of on the Internet. The first is We Were Burning, and the second is Industrial Innovation in Japan. The first is an easier book to read. According to that, Sharp was extremely quick off the block developing calculators, and amongst the first to productize (not invent) CMOS, so it's quite natural they would either license a Z80 design, or design their own chip. Neither of which would be good reasons to fake instruction names to look like a different processor.

Hi Shabaz,

As Appendices at the end of the 276 page PC-1600 Tech Ref Manual I found mnemonics, op-codes, and what have you of both the SC- and the

LH-processor. Not my cup of thea, really ... But maybe someone else finds the clues, required to answer the question: was LH-5801/3 a Z80

derivative, or not ?

For me Chapter 7 is much more evocative, and it confirms my belief all along, that not only 'Ol Blue Eyes did everything "My Way" ...

It is quite impressive what Sharp has integrated on-chip*, next to the processor 'core' - this goes for the Z80A derivative, as well as for the LH.

I've called what they have packed into this pocketcomputer "no mean feat". If you look at the features, you can say that again:

- 3 microprocessors, two 8-bit main CPUs (one emulating the PC-1500A a.o.) + one 4-bit subprocessor (I/O)

- 3 x 36 kB ROM

- RS-232C I/F

- serial optical I/F, 38.4 kbaud

- analog input (ADC)

- automatic power off with external wake-up from peripheral

- floppy and RAM-disk options

- 60-pin fully programmable system/expansion bus output

- 2 memory module slots

Impressive ? Sure ! A joy to work with (as a programmer or a user) ? Not really ... And that's a shame.

PC-1600 has never been able to replace PC-1500A in the market, possibly because it became the victim of its own over-complexity ?

At the time (mid eighties and on) Sharp had already her organizer concept ready, later shared in the PDA concept with Apple (Newton),

and so probably didn't care too much ... (PC-12xx, 14xx, E200, and E500 series thriving)

Cheers

Ray

* a.o. the complete port processor, LH-5811, of PC-1500 in the SC main CPU

Hi Ray,

It could be derived from the Z80, I really cannot tell one way or another.

I used the Z80 a lot in the home 8-bit computer era with plenty of machine code (I had no assembler) but I cannot recall much apart from a few instructions and op-codes that won't seem to leave the brain : )

The embedded 8-bit stuff I encountered later was mostly Motorola based (6805 and 6811 particularly) and a few other manufacturers.

Hi Shabaz,

Further to the Z80 discussion in relation to the Sharp PC-1600: reading the Technical Reference Manual, answers to several questions can be

found:  http://pockemul.com/Documents/PC1600/PC1600TechnicalReference.pdf .

First of all, the main CPU, SC-7852, is a Z80A-clone. Second: Sharp specifies LH-5801/3 for what they call the subprocessor; so early production

probably was equipped with the 'old' PC-1500A CPU, which was then later on replaced by an upgraded version, the LH-5803.

After that the LH-58xx series was obviously discontinued, in favour of their SC family of micrprocessors - maybe to improve Z80(A)-compatibility.

The best - most comprehensive yet concise - overview: https://sharppocketcomputers.com/index.htm#basic . As an aside: It is remarkable that

after the 4-bit SC dual processor in Sharp's first pocketcomputer, the PC-121x had been succeeded by the 8-bit LHs, 4-bit SC-processors were

used again in later models.

Where the master-slave operation in the PC-1211 worked flawlessly, cooperation between the SC-Z80A and the LH-subprocessor more often than

not led to system instability, up to complete crashes.

The main disappointment with the PC-1600 however was its substandard (for Sharp at least !) LCD. Cramming this 4 times bigger display plus an

extra full size PCB, etc. into the same case as the PC-1500 however, is of course no mean feat ...

Maybe taking a glance at mnemonics and opcodes in the PC-1600 Tech Ref Manual can bring our decission nearer as to the LH-5801 was a Z80

derivative, or not. Memory allocation of the SC-Z80 surely differs considerably from that of the LH-5801, yet addressing range is equal (512 kB),

thanks to the flipflop registers in the LH; the SC seems having to do a lot of bank switching in large applications ...

Cheers

Ray

Hi Shabaz,

Very interesting musings about Z80 and possible 'mimicry' ... And thank you for the literature suggestions.

I believe having gotten some idea of Sharp policy in the dozen or so years I've made a living out of their products in many applications.

Do share your viewpoint that a lot of Japanese manufacturers of the time had more than enough innovation capability of their own, in order

not having to rely on copying; they did however clever- and selectively enter into strategic alliances and joint ventures.

I was appalled to learn that the company was recently taken over by Foxconn, of all the lousy manufacturers of today ...

The Japanese goverment should be ashamed for not having done anything to prevent this - the company that produced the unique amber

EL-displays for the Space Shuttle and where Philips had to buy all their LCD patents !

Back to the good ol' eighties and Sharp policy: I still feel the only explanation that makes sense for the model number, (LH-)5801, is as follows.

Next to their OEM production of Z80 clones - LH080, etc. - they wanted a proprietary microprocessor design for their indeed innovative line of

pocket computers. However they did not want to isolate these products too much from the brands and models that had become well-known

market leaders, in order to reach the broadest possible acceptance. So they devised the number 5800, with a wink to the 6800; but in order

to prevent the impression that they would suggest to make a predecessor, or down-graded version, they made the number their own by changing

it into 5801. Speculative ? Sure, but have I "entered into the realms of phantasy" ?

There was btw a LH-5803, which was meant to emulate the 1500 in its successor, the PC-1600 in order to attain full SW-compatibility. (It didn't

work 100% - much like my XP Pro overlay on Windows 10; this was probably also the reason for the PC-1600 being a less stable system than the trustworthy 1500).

Cheers

Ray