8085 Development System

[River25]

Hi,

My favourite 8-bit processor is the 8085. It is a simple CPU, extremely easy to use in both hardware and software, and it can make a great microcontroller with just a pair of chips (8755 and 8155), and its on-board vectored interrupts are highly useful. Some years ago I decided to build a small 8085 system for development work. This comprised on the main CPU board, which attaches to a peripheral board, and the ability to route the buffered CPU signals, as well as the peripheral chip lines externally so they can be accessed easily for development work. Both boards were wire-wrapped. I like to wire-wrap things.

I wrote a nice monitor/debug program, based off the Intel SBC software, that allows me to do all the usual stuff like memory dump/edit, register dump/edit, comms testing, break points, hex file up/download, and numerous other functions that are useful when debugging code. I also put the whole lot into a home-built enclosure with a PC/AT type power supply and routed all the buffered CPU signals and peripheral chip signals out to the top of the box, all labelled and a large breadboard area so connecting up various devices etc would be simple and easy.

The system details are, 40K RAM, 16K EPROM (though it only uses 8k for the monitor/debug software), 2 x 8255 PPI for parallel IO, 8251 for serial comms, 8254 for timer/counter work, and an 8259 interrupt controller for any interrupt sort of work I might like to do.

All the above ports and signals are labeled and accessible on the top of the unit, along with all the necessary buffered 8085 CPU signals. I also routed spare IO and memory select signals and clock signals. Basically, to have every signal I could want to allow me to plug in whatever I want into the breadboard area and connect to the system to test hardware and software. Once all done and going I then move whatever I was developing into a dedicated system (or whatever it is I require), and that is how I use this system.

I am doing the same thing for a home brew 6502 system. It too will be wire-wrapped, and I have completed the hardware design and am about to commence wire-wrapping it up. I have done the software for it but won't know until I get the basic hardware connected how many bugs I need to fix. I also have done a small version for my 2650 CPUs. I have done the hardware design and got this one half built but via soldering and using a veroboard - similar to my SC/MP II SBC which I put up in another thread. I have plans to do a Z80, 6800/6802 and 6809 systems, all in the same manner and running similar software interfaces.

But this is about my 8085 system, so apologies for my wandering off topic there. Anyway, here are a couple of pictures of my home brew 8085 system, and you can see what I mean when I route the signals out into a breadboard area to facilitate development work. It's not a pretty system, but it does work very well.

river

[SiriusHardware]

A very nice 8085 dev kit.

The only experience I've had with 8085 programming was some code that I wrote probably 25+ years ago now to repurpose a microprocessor based front panel / control head which was fitted to PYE / Philips MX294 transceivers.

I didn't have an 8085 assembler so I wrote the code using a Z80 assembler and where I needed single byte 8085 specific instructions such as RIM and SIM I just placed the opcode for those inline with the code with a DEFB directive, with a 'RIM' or 'SIM' comment.

[Phil__G]

I still have a working SDK85 which is an 8085 devkit, its from way back teaching BTEC microprocessor based systems at sheffield poly
The topic was mostly assembler but I cant remember which one we used...

[Phil__G]

Found this in my stash:

[River25]

Hi,

Originally Posted by Phil__G

I still have a working SDK85 which is an 8085 devkit, its from way back teaching BTEC microprocessor based systems at sheffield poly
The topic was mostly assembler but I can't remember which one we used...

Some years ago I purchased on old busted up SDK-85 from eBay. Because it was broken the price was low. It is an interesting board, as it has a 16K S100 RAM card attached to it. Even more interesting is it must be a very early SDK-85 board because it has an 8085 and not the 8085A CPU. The original 8085 was quickly pulled from production to fix some timing glitches and was re-introduced as the 8085A. You don't see many 8085 CPU. Unfortunately, the one I have is in the plastic case. It would have been awesome to have a ceramic version. I fixed the board, and it works fine.

Here are a couple of pics; showing the S100 RAM card, which is mounted underneath the SDK-85 main board, as well as pics of the SDK-85 and its 8085 CPU.

river

[DrStrangelove]

I haven't programmed an 8085 since the demise of the Intel "Blue Box" MDS II.

Now I think about it there's a Blue Thunder PC card in the junkroom that pretends to be a Blue Box and runs the Intel Tools.

For the uninitiated this is an MDS II:

https://www.ricomputermuseum.org/col...lopment-system

The floppy diskette drive on the side is SSSD easily read by other machines.

The double drive that fitted on the top was DSDD in a format nothing else could read (without much jiggery pokery).

[TonyDuell]

I haven't programmed one for some years, I think the last time I wrote 8085 code was on a Tandy Model 100 laptop. But the processor is used in many DEC peripherals (R80 disk, TU58 DECtape II to name 2 I can see without getting up) and several other devices/instruments that I own. I do have a programmer which can handle the 8755 EPROM/IO chip too.

An 8085 in-circuit emulator is something I am always half looking for...

[DrStrangelove]

Ah yes, The Elephant's Trunk: the thing that connected the MDS II to the target.

I forget how many k that cost back in the late 70s.

[Ken G3XSJ]

Great to read about these. I built an SDK-80 kit c. 1975, writing the machine code programme which would evaporate when turned off. Later, I used the cream coloured cream 8085 development system with 8" discs. Would love to see and use another SDK-80 or 85.

Ken

[River25]

I have an Intel 230 MDS and a pair of Intel Model 430 MDS. The blue 230 is dead and I need to look into it and fix it. I think it is a screen issue more than a system issue. It runs twin 8-inch disks and I have the external twin 8-inch disk expansion also.

One of my MDS 430 models is dead. I know which board is dead and it is just up to me to try and fix it. The other 430 works fine. Both units have a full height 5MB (or 10Mb... I need to go check) HDD and a 5-1/4 inch FDD. They both run ISIS and I have all the relevant software for PL/80, Assembler, PL/M, x86 and x51, along with the necessary 8051 and 8085 ICE modules. I admit I haven't used the ICE modules yet.

I purchased the 430 units about 20 years ago. I paid for the working one and the broken one, along with a box of software (both in 8-inch and 5-1/4-inch diskettes) and manuals and it cost me $600. Inside one of the manuals was the initial sales ticket, dated 1986, for $146,000 or something like that! Certainly, wasn't a cheap system back in its day. However, like so many other things, the ubiquitous IBM PC was given the necessary hardware board and software to do the same function but at a much better price point. Expensive, dedicated systems like the MDS series couldn't compete and Intel shutdown that division.

Intel made a small portable MDS machine, called the iPDS. I have one of those and it is supposed to be able to run CP/M, so I will see how that goes. It works fine, but I need to check if I have the relevant iPDS boot disks. Intel used some funky hard encoding or MMFM or something on their diskette drives, so it's not a simple task of throwing in any old diskette and thinking it will work.

river

[DrStrangelove]

Oh, I just remembered that the later white MDS used a weird format for the floppy: Track 0 was SD, the rest of the diskette was DD.

The Blue Box could be persuaded to run CP/M, having disassembled CP/M you can tell it was written in PL/M.

What I found odd was the lack of a checkdisk for the Blue Box: we had lots of interesting problems with corrupted floppies until I wrote a checkdisk that ran on a General Automation 16-220.

Then they made the GA obsolete & the problems returned.

[duncanlowe]

This was my only experience with 8085. Used for my final year project. The development system was a previous years group project. My project was to produce an interface between various computer devices (machine vision system, XY table, PC) but ended up being mostly debugging the flawed development system. One particular flaw was they seemed to introduce a new opcode: RRC (Random Register Corrupt) which would appear to suddenly change the values of all of the registers at once to unrelated values to the actual line of code.

[River25]

I am more a hardware guy than software, but in case you are interested, here is the main menu for my 8085-development system, so you can see the various commands it can do. I have used up most of the alphabet, and there are a few "spare" commands available, which I have reserved with an * for future use. It allows for most things one wants for simple development work, and some existing functions I have slated to be enhanced - like more than one breakpoint, etc.

As I am designing/building a similar system, but based on the 6502, I will try and use the same menu format, where possible. This will also apply to the future boards I aim to do, which includes a 6800/6802, Z80 and 6809. I might even do an 8080 board because it's such a cool old processor and it got me started into the world of microprocessors.

I may do the same menu for the home built 2650 system, but I need to finish wiring it up and then commence on the software side before I determine if it will be the same. And, although my SC/MP system is built, I am still doing the software side of it, and I will be using it for a dedicated function, which means I might need to build another SC/MP system for general SC/MP development and "play around".

Anyway, attached is the menu for V2.13 of my 8085-development system.

river