Is anyone interested with the Z80?

COMPACT  wrote:

 

The native mnemonics have been made to look like 6800/6500 style ones.

 

Interesting. For what reason would they do that? So it can look like a 6800/6500 derivative too? Or some other reason?

The CPU used for the PC-1500 is the LH5801. The native mnemonics have been made to look like 6800/6500 style ones.

Here is a quick partial cross reference between its mnemonics and Z80 equivalents.

http://www.pc-1500.info/Data/LH5801-ASMCodes_Sharp.htm

That's only a partial list of undocumented instructions.  There are various sets posted around the Internet including Z80 Undocumented Instructions .

Also be aware that some instructions are used for alternate purposes of later generation Z80s and derivatives such as the Rabbit 2000, Z180, ez80 etc.

For example the relatively useless LD L,L (0x6D) is not supported by the eZ80.

I concur those don't look like Z80 comands.

As an aside, when playing with my ZxSpectrum I found an interesting scenario when I was stepping through some code. It ran fine at full speed but errored in the debugger. There turned out to be a couple of commands that the chip knew about but the debugger (and documentation) did not.

Turns out that the undocmented commands are now documented

http://www.worldofspectrum.org/z88forever/dn327/z80undoc.htm

One also has to remember that R650x and Z80 had altered instruction sets to evade intellectual property claims.

Sharp did make Z80 products and to me the PC-1500 looks like a Z80 inspired CPU with the index registers missing (like the gameboy CPU) and altered object code and a disguised instruction set.

e.g. BC = X pair and DE= Y pair.

The Texas Instruments TI-84 Plus CE Calculator that does have a eZ80 (a Z80 derivative) in it.  With it one can play Gameboy and other games with it.

The processor itself is running at 48MHz but is using wait states to interface its slower memory and i/o.

If you do have one, don't upgrade to the latest firmware because it places unwanted scholastic restrictions upon it.

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RE: Is anyone interested with the Z80?

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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.

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 everyone,

I stumbled on these old beauties today,

Good ole 68,000uF 16VW capacitors with screw terminals as used for S-100 Bus systems.

These capacitors are the size of Soda Pop Cans and are used as filter capacitors for the unregulated +8V power supply.

Back in this era the power supplies were comprised of a giant transformer, full wave diode bridges and large filter caps.

Transformers had 3 sets of secondary windings. One for 8V with a large current rating (anywhere between 5-30A) and two 12V outputs with about a 1A current rating.

Every S-100 board had its own onboard voltage regulators that decanted power from the common -12V, +12V and + 8 V power supply lines.

It could take next to forever for an unpopulated S-100 frame for the power to dissipate.  It was common to install bleeder resistors across these capacitors on test S-100 power supplies for faster power dissipation.

That's really quick to write your own BASIC!

Did you know that 8080 Microsoft BASIC was written on a PDP-10?

Please post some pics, vids and schematic diagrams of your new system in action.

I get many of my components from Element14!

I hunt around for obsolete components that are not stocked by Element14 but beware of Chinese counterfeits!

Omg. Doesn't sound like much, but I actually have a working serial interface working with basic working. Thanks for everyone's help but asking my somewhat dumb questions.

Where do you people usually get your components and parts from?  I live in Connecticut, USA. I have been ordering from jameco. They are located in California.  Shipping is usually 4-5 days. Mouser is closer being in the mid West . Also digikey is in the same location. What area your experiences with these places or others in the us?  Shipping is usually $5 from jameco.

Thank you again. I'm sure I'll have more questions, but I finally have something working and doing something. 

With an NMOS Mostek Z80 (and with many others) with an oscilloscope confirm that the CPU Clock signal maximum is at least Vcc- 0.6V and below Vcc + 0.3V This is different to the standard Mostek NMOS Z80 signal levels of 2.0V.

It's stipulated on page III-72 of the Mostek Z80 Microcomputer Data book.