Celebrating the SCM for untangling 8080 and Z80 syntax

[James Harland]

Hi everyone, 

This is not a query, just a quiet celebration of the usefulness of the Small Computer Monitor. So today I've been working through the Leventhal 8080/8085 book, and getting some of the sample routines from there working on my Soviet Microtrainer (functionally identical with the Hewlett Packard 5036A). 

So things were going great, but I was worried that I was going to muddle up my Z80 learning with all the different acronyms in 8080. But SCM to the rescue! I realized I can enter the same hex code on the RC2014 as I have been doing on my 8080 machine, then simply use the D(isassemble) function to see the Z80 syntax for the same operations.

So now I'm happily going through this workflow, and revising my knowledge of Z80 syntax, whilst also putting the RC2014 through its machine code paces.

So thanks again to Spencer for putting this lovely combination of hardware and software together!

James

[James Harland]

I now see that Leventhal made an almost identical book for the Z80, and the sample programs are also the same, so I can check to see how the conversion went there too!

[Spencer Owen]

Hi James,

The Leventhal books are great. Well, I don't have the 8080 one, but the Z80 one is great. My go-to book though is Programming The Z80 by Rodnay Zaks, so that might be worth looking out for.

Thanks for the compliments on the hardware. I can't take credit for the software though. The SC in Small Computer Monitor also stands for Steve Cousins. So any thanks must go to him too.

Spencer

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[Alan Cox]

On Sun, 9 Nov 2025 at 13:33, James Harland <harla...@gmail.com> wrote:

I now see that Leventhal made an almost identical book for the Z80, and the sample programs are also the same, so I can check to see how the conversion went there too!

The same is true for most of the other books. Leventhal wrote one good book then ported it which actually makes it very handy as a set of cross references.

There's an 8080 | Z80 chart here

https://retroprogramming.it/2021/02/8080-z80-instruction-set/

 

[Michelle Lawson]

Interesting tool. Given the 'disclaimer', the fact that that page could go away as well, and since I'm always looking for some code to write, I'm thinking about writing a program that would allow me to search on a mnemonic, or a machine code value, or <whatever>, and then have it display the whole line of data from that page. If anyone might be interested in using it once I write it, you are sure welcome to it. I will also list the webpage and credits in the program as well.

[Phillip Stevens]

On Sunday, 9 November 2025 at 20:32:59 UTC+8 James Harland wrote:

So things were going great, but I was worried that I was going to muddle up my Z80 learning with all the different acronyms in 8080. But SCM to the rescue! I realized I can enter the same hex code on the RC2014 as I have been doing on my 8080 machine, then simply use the D(isassemble) function to see the Z80 syntax for the same operations.

If you’re interested in 8080/8085, there’s actually 8085 Module for the RC2014 Pro or Classic. And it supports all the standard RC2014 Modules, because it has a Z80 bus interface. There’s also a BASIC and a CP/M available for it.

https://groups.google.com/g/rc2014-z80/c/qo7nfDZmY-k

I’m AFK mainly, so currently you can order PCBs directly from Seeed Studio.

https://www.seeedstudio.com/8085-CPU-Module-for-RC2014-g-1345971

I use the z88dk assembler for cross assembly. It understands both Intel and Zilog interchangeably. And can produce code for either (plus a lot of other machines too). For learning purposes there is a “strict” mode that turns off all the synthetic code generation and undocumented instructions, which are useful otherwise for unifying code.

https://github.com/z88dk/z88dk/wiki/Tool---z80asm

The complete list of operations and codes is here.

As a useful reference across all the 8080/Z80 derivatives.

https://raw.githubusercontent.com/z88dk/z88dk/master/src/z80asm/dev/cpu/opcodes.txt

Cheers, Phillip

[James Harland]

That chart is really useful, thank you! 

[James Harland]

I'd certainly be interested once you have it up and running, thanks!

[James Harland]

Having installed and got used to using a separate 8080 assembler at the weekend, I did wonder if there were one which could do both at the same time. I'll certainly check out z88dk, thanks for the recommendation! The extra 8085 board looks cool!

[Peter Onion]

If you want to go "old school", then M80 and L80 are one way.  I used them exclusively  back in the 1980s so I have a nostalgic attachment to them.

I've also just come across ZSM (while fixing my problems with qterm), which has a pretty neat "driver" called ZC which will selectively assemble source .Z files depending on the presence of a .BAK file, so it only rebuilds files that have been edited since last run.  It does however then delete the .BAK files so there's no "going back" if it all goes wrong.

PeterO  

[David Lochlin]

Here's a link to a pdf copy of the Rodney Zaks book.
https://archive.org/details/ptz80/mode/2up?q=programming+the+z80

Dave

[Ed Silky]

Thanks Dave. I used to have a copy of this book, thanks for the link. I did a lot of Z80 programming in the '70s/'80s, so my Programming Manual (from Zilog) is well-worn and dogeared (still in my bookshelf), but it is nice to have an alternate text to review from time to time.

-Ed