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UncleBinary
September 24th, 2006, 06:23 PM
Im trying to make a 8088 based computer into a Altoids bin.Its going to have a 8 bit parralel port,a analog port for music,and port for a keyboard a and a mini screen.Along with 128k*8 RAM and 128k*8 ROM.ANY suggestions for parts (must be small).Should be finished in 3 months.

daflory
October 6th, 2006, 09:10 AM
I'm very impressed...but that is going to be a very tight squeeze. The 8088 requires a fair number of support chips.

I think there are newer (but still old) 8088 clones or Intel models that integrate the memory controller, DMA, etc. with the processor. You should look into those too.

IBMMuseum
October 6th, 2006, 10:25 AM
I'm very impressed...but that is going to be a very tight squeeze. The 8088 requires a fair number of support chips.
Ever see an Intel 8088AN? That is where a hermetic seal is put over the top of the CPU on the circuitboard. Probably about a half inch all around, and less than 1/8th inch bulge from the PCB plane. I've got two duplicates that are on a SIMM-like board with a ROM chip for some sort of laptop.

I think there are newer (but still old) 8088 clones or Intel models that integrate the memory controller, DMA, etc. with the processor. You should look into those too.
You are thinking of the 80186/80188 CPUs. Very rare to find PCs built around them, but some circuit real estate could be regained by using one. For an even smaller form-factor something like an NEC V40 could be used. Had a circuit board from a fax machine (with a little RAM & ROM) that used one.

Mike Chambers
October 6th, 2006, 06:23 PM
wow........ thats a pretty interesting project! i'd like to see pictures of it as you go along :p

good luck with it, as has been said that's a very tight squeeze. it will probably get very hot, too. maybe the altoids tin PC can double as a miniature stove!! the Sony PSP has nothing on your 8088 altoids tin.

i would also highly reccommend sticking an ethernet adapter in there if you can do it. maybe an ne1000 compatible or a 3c507

IBMMuseum
October 6th, 2006, 09:33 PM
Ever see an Intel 8088AN? That is where a hermetic seal is put over the top of the CPU on the circuitboard. Probably about a half inch all around, and less than 1/8th inch bulge from the PCB plane. I've got two duplicates that are on a SIMM-like board with a ROM chip for some sort of laptop.
Whoops, I mean 8088AL. The card is for a Daewoo laptop, and has the name "Wildcard 88-N" silkscreened in script. Probably that is what got me confused.

It is in an "A" & "B" part. "A" is just smaller than 1/2" square. "B" is about 5/8ths of an inch square. Copyright Intel '78, '86.

Chris2005
October 7th, 2006, 11:02 AM
"Ever see an Intel 8088AN? That is where a hermetic seal is put over the top of the CPU on the circuitboard. Probably about a half inch all around, and less than 1/8th inch bulge from the PCB plane. I've got two duplicates that are on a SIMM-like board with a ROM chip for some sort of laptop."

I was of the persuasion that they all are hermetically sealed. Note I didn't say actually believed (on good authority) they were. Please edumucate me :)

"You are thinking of the 80186/80188 CPUs. Very rare to find PCs built around them, but some circuit real estate could be regained by using one. For an even smaller form-factor something like an NEC V40 could be used. Had a circuit board from a fax machine (with a little RAM & ROM) that used one."

I have the Intel 80c186/80c188 Evaluation Board, and in fact need docs and whatnot for it. It's a far cry from a peecee mobo, takes up as much real estate as a 5.25" drive pretty much. There were MANY sbc's based on the 80188 or 80186. Granted most of them were single purpose, and would fail short (very) of a true peecee architecture. And to conclude that the functions that were integrated on die which were present in discrete form on a peecee can automatically take their place is somewhat faulty. Port addresses and the like would differ. I believe that although the Tandy 2000 for instance used the 80186, it ignored those functions and simply utilized it as a fast 8088 (8086 actually). That particular mobo had a pretty high chip count, but we'd also need to keep in mind that floppy, some video, serial, etc. stuph was built right in.

IBMMuseum
October 8th, 2006, 12:44 PM
I was of the persuasion that they all are hermetically sealed. Note I didn't say actually believed (on good authority) they were. Please edumucate me :)
I mean by hermetic black goop. See attached picture (copyright date is '78, '86). And one of the whole Wildcard assembly too.

Chris2005
October 9th, 2006, 03:12 PM
when you see those blobs, often that's just a means of mass producing an integrated circuit. My Radio Shack chess game (handheld) has one of those "chips" inside. I thought that was a way of cutting down on packaging costs. Lots of cheap calculators will have them also. I don't know though. What do I know...

IBMMuseum
October 10th, 2006, 04:37 PM
when you see those blobs, often that's just a means of mass producing an integrated circuit. My Radio Shack chess game (handheld) has one of those "chips" inside. I thought that was a way of cutting down on packaging costs. Lots of cheap calculators will have them also. I don't know though. What do I know...
But this is a version of an Intel 8088 CPU I have seen nowhere else (BTW, Bob Grossblatt's "8088 Project Book" is an excellent reference for this sort of thing). Probably Intel's only foray into this package type, at least for x86. I know that it was common practice with some other manufacturers.

Thrashbarg
October 15th, 2006, 03:55 AM
here's my attempt at an 8088 (V20, min mode) single board computer. It currently has 128K RAM, 32K ROM, a serial port and a primitive hard drive interface. It's not quite done yet, just need to get a MAX232 for the serial port.

Next i'm going to build an 80286 single board computer.

Pictures:

http://kaput.homeunix.org/~thrashbarg/8088v20_1.jpg
http://kaput.homeunix.org/~thrashbarg/8088v20_2.jpg

Terry Yager
October 15th, 2006, 07:27 AM
Thrashbarg,

Great projects, but do you have more details of the construction, including schematics, ROM source, construction notes, whatever, so that others may follow your designs? (I'd love to build one of my own).

--T

IBMMuseum
October 15th, 2006, 01:23 PM
here's my attempt at an 8088 (V20, min mode) single board computer... Pictures:
http://kaput.homeunix.org/~thrashbarg/8080_1.jpg
http://kaput.homeunix.org/~thrashbarg/8080_2.jpg
I understand your other, main project is the 8080 (and well documented at that, Thank You for the contributions), but are the picture names you have set up a typo? And why not name them for the V20? What are the 8080 opcodes that the NEC CPUs (V20, V30, V35, V40, V50) are able to emulate if you know?

IBMMuseum
October 15th, 2006, 01:38 PM
Great projects, but do you have more details of the construction, including schematics, ROM source, construction notes, whatever, so that others may follow your designs? (I'd love to build one of my own).
Mentioned earlier, Robert Grossblatt's "The 8088 Project Book" (ISBN 0-8306-0271-2, or paperback ISBN 0-8306-3171-2) is an excellent reference for putting something like this together. And great humor you won't commonly see from other authors. For not starting from scratch there are cards that have 8088 CPUs from discarded Xerox Memorywriters (which had a monochrome display & diskette drives in a few versions).

Terry Yager
October 15th, 2006, 02:01 PM
Actually, I'm more interested in the 8080 projects. I've not even begun to cut my teeth on 16-bit stuff.

--T

Thrashbarg
October 15th, 2006, 06:23 PM
I understand your other, main project is the 8080 (and well documented at that, Thank You for the contributions), but are the picture names you have set up a typo? And why not name them for the V20? What are the 8080 opcodes that the NEC CPUs (V20, V30, V35, V40, V50) are able to emulate if you know?

oops...

According to the datasheet the V20 has full 8080 emulation.


Actually, I'm more interested in the 8080 projects. I've not even begun to cut my teeth on 16-bit stuff.

16-bit stuff isn't that hard. It's just like 8-bit, only more powerful.


I'll make schematics of the 8088/V20 now and post them.

Terry Yager
October 15th, 2006, 08:05 PM
oops...

According to the datasheet the V20 has full 8080 emulation.



16-bit stuff isn't that hard. It's just like 8-bit, only more powerful.


I'll make schematics of the 8088/V20 now and post them.

But, I'm still a babe-in-arms...
One question, tho: Why did you strap the V20 to Minimum Mode? Is it just easier to interface to that way (lower chip count, etc)?

--T

Thrashbarg
October 15th, 2006, 11:05 PM
One question, tho: Why did you strap the V20 to Minimum Mode? Is it just easier to interface to that way (lower chip count, etc)?

Yes, in maximum mode it needs another chip to decode the R/W and other signals.

Here's the scheamtic:

http://kaput.homeunix.org/~thrashbarg/8088.png

It looks complicated, but the chip count is low (5 support chips for the 8080, 4 chips for address decoding, the rest are RAM/ROM and I/O devices).

I got the 8284 clock generator from the XT motherboard I stripped most of the components off. You may need to desolder it, mine was in a socket. If you want to run in maximum mode (it doesn't change the code or speed, just the number of signals available), you'll need to get the 8288 from a motherboard too. The XT runs in maximum mode.

Anything else should be answered in the 8088 datasheet which you can google ;)

Mike Chambers
October 16th, 2006, 09:31 AM
Yes, in maximum mode it needs another chip to decode the R/W and other signals.

Here's the scheamtic:

http://kaput.homeunix.org/~thrashbarg/8088.png

It looks complicated, but the chip count is low (5 support chips for the 8080, 4 chips for address decoding, the rest are RAM/ROM and I/O devices).

I got the 8284 clock generator from the XT motherboard I stripped most of the components off. You may need to desolder it, mine was in a socket. If you want to run in maximum mode (it doesn't change the code or speed, just the number of signals available), you'll need to get the 8288 from a motherboard too. The XT runs in maximum mode.

Anything else should be answered in the 8088 datasheet which you can google ;)

http://rubbermallet.org/1337.jpg

thats cool as hell, that schematic isnt that complex. i might build a little homebrew 8088 just for kicks. the CPU on my TURBO-XT motherboard is in a socket so no unsoldering will be required.

now, what about an ISA bus? :/

actually i'd hate to take that CPU off my board, i'll probably just buy a spare 8088 CPU on ebay... they're about $5

IBMMuseum
October 16th, 2006, 11:52 AM
According to the datasheet the V20 has full 8080 emulation.
Cool, meaning that the V30 (8086 replacement), V40 (80188 replacement), & V50 (80186 replacement) should as well (there is some Z80 PC adapters on eBay that are supposed to make the PC able to run CPM, but if you have an NEC CPU in the system it could do the same?). Getting back to the original thread, I had desoldered a small form-factor V40 from a FAX board, meaning that it should be in stock somewhere or able to be pilaged from a board. This would be an 8-bit CPU (unknown for the minimum/maximum setting) with a few support chips onboard to make it so the OP could do his project.

Terry Yager
October 16th, 2006, 03:56 PM
I have a couple of different programs for running CP/M on the NEC V-series. I have run both on my V-40 based LittleBoard PC. I also have them running on my ZEOS Pocket PC (V-20), and a couple of Tandy laptops.
The old-school Z-80 boards used to be just about the only viable option for running CP/M-80 on a PC, but with today's super-fast hardware, most software-only emulators run acceptably well.

--T

IBMMuseum
October 16th, 2006, 04:45 PM
...Getting back to the original thread, I had desoldered a small form-factor V40 from a FAX board, meaning that it should be in stock somewhere or able to be pilaged from a board. This would be an 8-bit CPU (unknown for the minimum/maximum setting) with a few support chips onboard to make it so the OP could do his project.
To show how small this version of the NEC V40 is I have attached a picture (alongside an IBM-labeled 8088 CPU that is a regular-sized 40-pin DIP). This V40 will be thinner on the PCB than the 8088 is alone in height, and about 40% of the width. Just the fact of including a few of the 8-bit support chips needed for the 8088/V20 would make it worthwhile too...

Chris2005
October 16th, 2006, 05:21 PM
if you use the v40 or v50, presumably the onboard peripherals (replacements for external ic's that are typically found in 8088/8086 based systems), the i/o addresses of those functions will differ, so you'd be sacrificing some degree of IBM compatiblity. If that's what you were looking for.
There are other books besides Grossblatt's. I have a few of them, probably in storage, but if anyone is dying to know, pm or e-wail me. I'll dig them out. Eventually...
There's always the Radio Electronics Robot Brain (circa 1988). A series of projects aimed at producing a robot thing. Really just a set of wheels with a forklift fork thing, maybe an arm. Had an 80188 uP. Probably not extremely peecee compatible (see 1st paragraph) but fun nevertheless. It had complete artwork right in the mag too. Been meaning to try my hand at etching my own board from that, but I've been put off...
You can think of the 8088/86 in minimum mode like an 8085, sort of. But can access the full 1meg of memory. The Peanut and Victor 9000 were wired into minimum mode. "www.micro-zone.com" Brian was working on a retrofit (no pun intended) to interface an 8087 to the Peanut. Of course it would need reconfiguring in maximum mode (no ancillary processors on board in minimum mode), and since the Peanut was hard wired in minimum mode...you guess it, the board would have to plug into the 8088 socket, and have a nutha 8088 on board. Something like that. Leave me alone already.
Thrashbarg...cool stuph! ;)

Chris2005
October 16th, 2006, 05:22 PM
o, Thrashbarg. Cool stuph! ;). I don't have to tell you that most peeps would have wire-wrapped the connections.

IBMMuseum
October 16th, 2006, 09:24 PM
if you use the v40 or v50, presumably the onboard peripherals (replacements for external ic's that are typically found in 8088/8086 based systems), the i/o addresses of those functions will differ, so you'd be sacrificing some degree of IBM compatiblity. If that's what you were looking for...
There are PC-compatible systems using the V40 out there. I have one myself (a Packard Bell unit). Someone else here talks about their laptop using one (and I spotted this today, but please don't drop this post in "Auctions" ;) : http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=300037906020).

The original poster said: "Im trying to make a 8088 based computer into a Altoids bin.Its going to have a 8 bit parralel port,a analog port for music,and port for a keyboard a and a mini screen.Along with 128k*8 RAM and 128k*8 ROM.ANY suggestions for parts (must be small).Should be finished in 3 months."

This version of the V40 (I didn't mention the one I have is 10MHz) fits the "small" bill. For the functions he wants the V40 onboard support chips (DMA controllers, interrupt controller, timers, clock generator, DRAM refresh control unit, no NPU support) will do just fine.

Chris2005
October 17th, 2006, 10:09 AM
maybe peecee compatibility wasn't his aim, so that's an assumption on my part. I don't know how your unit gets away with full peecee compatibility. Perhaps it ignores the integrated peripherals? I don't know all that much about v40s and such, just assumed they were like the 80188/80186, who's on chip things differ in port assignments from a peecee.
Maybe you should look into the PBell thing and let us know.

IBMMuseum
October 17th, 2006, 11:35 AM
...I don't know how your [Packard Bell with V40] unit gets away with full peecee compatibility. Perhaps it ignores the integrated peripherals? I don't know all that much about v40s and such, just assumed they were like the 80188/80186, who's on chip things differ in port assignments from a peecee.
Packard Bell using NEC chips is no big surprise (the companies were affiliated until just very recently), but it is highly unlikely that a motherboard would be designed with a certain CPU to ignore some of the circuitry in place (if that were even possible). Why wouldn't they just use an 8088? And for the V40 laptop too, where space is at a premium?
Which integrated peripheral chips differed in port assignments for the 80186/80188 from the standard PC layout? Much of the 80186/80188 failure to be used in the PC industry was just a fact of being too little, too late. The irony being that they were commonly used on many controller devices later.

Maybe you should look into the PBell thing and let us know.
Sure, I'll get right on it...

Chris2005
October 17th, 2006, 11:44 AM
the integrated peripherals of at least the original 80186/80188 were meant to take the place of some of the discrete ic's typically found on say a peecee mobo. And as you probably know, they're assigned port addresses and whatnot (or should I say the discrete components are when they're hard wired into the mobo). These "integrated peripherals" are going to inhabit different parts of the i/o space as compared to the peecee's discrete-peripherals. I'm sure you're no stranger to an IBM mobo - the ic's I'm referring to all begin with the number "8".
That's my understanding. I'm not an engineer to say the least.
There have been many "other" releases of these chips, and it's not unbelievable that some of these could have reassigned port addresses. And the NEC chips are different animals altogether (similar masks I'm sure, but I'm sure they could have had the license to modify them here and there).
And come to think of it, I have a later Ampro Little Board PC thing, which has a v40, and that is *I'm pretty sure* "100%" peecee compatible.
You're wasting time LOL LOL

BY the way, are your initials S.A. If ya don't mind me asking?

kb2syd
October 17th, 2006, 12:02 PM
Packard Bell using NEC chips is no big surprise (the companies were affiliated until just very recently)

And the guy that now ownes the packard bell name also owns some IP from Tandy. He purchased it from Samsung who got it when AST went belly up.

What a tangled web we weave.

Chris2005
October 17th, 2006, 12:03 PM
hoser who cares? What does that have to do with anything? Sheesh

kb2syd
October 17th, 2006, 12:26 PM
hoser who cares? What does that have to do with anything? Sheesh

I care....

All the crossbreeding and inbreeding leads to quite a tangled IP web. I happen to be facinated by where all this winds up in the end.

If you care don't then ignore my posts. I know you know how to do that. Takes all of a second to scan by it.:p

Chris2005
October 17th, 2006, 12:28 PM
I remember you saying that you never take anything I say seriously. Being that you're taking me seriously all of a sudden...should I be feeling important?

kb2syd
October 17th, 2006, 12:32 PM
Thanks for mentioning it. I'm in a foul mood today. I think we should retire this part of the thread to PM. We can hurl insults at each other and not offend the delicate senses of the masses...

:)

IBMMuseum
October 17th, 2006, 03:28 PM
hoser who cares? What does that have to do with anything? Sheesh
I just remembered what I like about my newsgroup reader that I dont have here...

IBMMuseum
October 17th, 2006, 04:10 PM
the integrated peripherals of at least the original 80186/80188 were meant to take the place of some of the discrete ic's typically found on say a peecee mobo. And as you probably know, they're assigned port addresses and whatnot (or should I say the discrete components are when they're hard wired into the mobo). These "integrated peripherals" are going to inhabit different parts of the i/o space as compared to the peecee's discrete-peripherals. I'm sure you're no stranger to an IBM mobo - the ic's I'm referring to all begin with the number "8".
That's my understanding. I'm not an engineer to say the least.
There have been many "other" releases of these chips, and it's not unbelievable that some of these could have reassigned port addresses. And the NEC chips are different animals altogether (similar masks I'm sure, but I'm sure they could have had the license to modify them here and there).
And come to think of it, I have a later Ampro Little Board PC thing, which has a v40, and that is *I'm pretty sure* "100%" peecee compatible...
I remarked above that the integrated peripheral chips were "DMA controllers, interrupt controller, timers, clock generator, DRAM refresh control unit" and you tell me the chip numbers begin with an "8" (which they do) to narrow it down for me? You state that they will be in different I/O port locations than the PC architecture but give no further information to the source of that data? Maybe the I/O port locations of much of those peripheral chips could be mapped (where the ROM code of whichever system the CPU is in sets up the port location according to the circuit's design) instead of hard-coded?

Think more flexibly. There is a reason that these CPUs with integrated peripheral chips were used in many different designs, including a few PC-compatible computers. My final comment here is that I think the V40 will do what the OP wanted in a small design.


You're wasting time LOL LOL
BY the way, are your initials S.A. If ya don't mind me asking?
I took this in context with other comments that I was being asked whether I was a "Smart Ass" or "Stupid Ass"...

Chris2005
October 18th, 2006, 05:24 PM
"I remarked above that the integrated peripheral chips were "DMA controllers, interrupt controller, timers, clock generator, DRAM refresh control unit and you tell me the chip numbers begin with an "8" (which they do) to narrow it down for me?"

Whoops guess I missed that part. Hey to err is human...

"You state that they will be in different I/O port locations than the PC architecture but give no further information to the source of that data?"

Just understand it was on real good authority. The dude is also an a leading authority on adhesives. Uses 'em all the time...

"Maybe the I/O port locations of much of those peripheral chips could be mapped (where the ROM code of whichever system the CPU is in sets up the port location according to the circuit's design) instead of hard-coded?"

The discrete components of a peecee mobo could take on any number of port addresses. But that's irrelevant. And I'm here asking the question, are the port assignments of the integreated peripherals re-assignable? And if so by firmware?

"Think more flexibly. There is a reason that these CPUs with integrated peripheral chips were used in many different designs, including a few PC-compatible computers. My final comment here is that I think the V40 will do what the OP wanted in a small design."

The 80186/80188 were used OVERWHELMINGLY in sbc's and the like. The 80186/80188 showed up in precious few peeceez. This much I know. And with the exception of 1 (that I know of), they were all pretty incompatible. And I did mention that I myself, even I, own a small form factor peecee based on the v40 that is probably fully compatible. So why the debate?


"No, they're "F.O"..."

I won't stop to contemplate if those are your actual initials or not. Because if I do, it might lead me to believe you're actively trying to be impolite.

Terry Yager
October 18th, 2006, 06:04 PM
Just don't get PO about the FO...I'm pretty sure it wasn't personal.

--T

mbbrutman
October 18th, 2006, 06:15 PM
hoser who cares? What does that have to do with anything? Sheesh

Chris,

What the heck was the motivation behind that post?

It is not called for. Chill out.

chuckcmagee
October 18th, 2006, 07:27 PM
I care too. It's super interesting, all the history of the IP addresses. I learned all about it when I had to do my own DNS at work. Found all about ARP and RARP and MIL, etc. Was very interesting! I even learned how all those DNS servers cooperate with each other and why it takes HOURS for the "DNS Tree" to stabilize again after some lookup changes.

Terry Yager
October 18th, 2006, 07:44 PM
I care too. It's super interesting, all the history of the IP addresses. I learned all about it when I had to do my own DNS at work. Found all about ARP and RARP and MIL, etc. Was very interesting! I even learned how all those DNS servers cooperate with each other and why it takes HOURS for the "DNS Tree" to stabilize again after some lookup changes.

Aarrgh! I'm in AcronymHell! I thought he meant IP as in 'IntellectualProperty'...

--T

chuckcmagee
October 18th, 2006, 09:53 PM
Hehe, upon rereading it myself, he did mean that. Anyway, I care either way :p

Terry Yager
October 19th, 2006, 07:38 AM
Hehe, upon rereading it myself, he did mean that. Anyway, I care either way :p

MeToo! The human brain cannot absorb too much useless trivia. Ya never know, Jeopardy could call any day now...

--T

Chris2005
October 19th, 2006, 04:05 PM
Mike B. - it's been said by Kelly himself that he never takes me seriously. I guess I was wrong...everyone's entitled to their moods. I got into the habit of calling him "the hoser" cuz while I was in NJ, and part of that other group, we used to poke phun at him from living...almost in Buffalo, which is just next to Canada. Actually just way up north in the state, further then anyone else.
No harm was meant. Typically he doesn't react to my ribbing at all.

mbbrutman
October 19th, 2006, 07:09 PM
Lets just make sure we all try to keep it civil. And remember the golden rule about posting - if it takes less than 30 seconds to post, it probably shouldn't have been posted.

Chris2005
October 20th, 2006, 11:23 AM
suuuuuure dude! I'll remember it! :)

UncleBinary
December 3rd, 2006, 05:46 PM
Sorry for not being here in so long but I decided not to use the 8088 and to either use the z80a running at 4Mhz or a nec v15 UPD70108-8 running at 8Mhz and im not sure which.Anyone have a website name that gives info about them?And does anyone know a website which sells IC's?Someone please check to see if this equation to find RAM speed is right. 1/(1/ns)

Terry Yager
December 3rd, 2006, 06:46 PM
Have you seen this page?

http://www.geocities.com/SiliconValley/Peaks/3938/z80_home.htm

--T

Thrashbarg
December 5th, 2006, 01:27 PM
Have you seen this page?

http://www.geocities.com/SiliconValley/Peaks/3938/z80_home.htm

--T

Also at http://z80.info. Little easier to remember ;)

You'll find 8-bit processors easier to use if you haven't made one before. When I tried the 8088 after a few 8-bit machines I found it to be quite difficult.

UncleBinary
December 5th, 2006, 02:02 PM
Im new to making computers (havent made one yet).Im looking for a simple easy to make one to get me started.There is a site called www.jameco.com that is selling a 100 piece assortment of microprocessors , PALs , EPROM, RAMs, PROMs. Do you think its worth it for 12.95?I need a single board system with a mini keyboard,screen,at least 8k of EPROM and 8k or SRAM.Any suggestions for parts from jameco?

Thrashbarg
December 5th, 2006, 02:32 PM
There is a site called www.jameco.com that is selling a 100 piece assortment of microprocessors , PALs , EPROM, RAMs, PROMs. Do you think its worth it for 12.95?

I don't know what devices they're selling but YES


I need a single board system with a mini keyboard,screen,at least 8k of EPROM and 8k or SRAM,and maybe a spare parrelel port.Any suggestions for parts from jameco?

The easiest way to get a screen is to use a UART (I found the Intel 8251 to be easy, with some example code on z80.info) and attach it to a regular PC running a terminal program such as Kermit or Hyper Terminal (which I hate).

For RAM and ROM, you might as well implement 32K ROM and RAM, A because it's easier and B you'll have more space.

It's easier because you can attach an inverter (74LS04, pin 1 for input and pin 2 for output) to Address 15 of the microprocessor, the inverted signal can be the Chip Select for the upper 32K of the 64K address space, the non inverted signal is the lower. There might also be some other logic necessary if you're going to use a Z80, because they have separate address spaces for I/O ports and memory which also need to be decoded.

In this case, this is what I think could work. Get yourself a 74LS32 Quad OR gate. Attach the output of one of the gates (say pin 3) to the RAM and another (say pin 6) to the ROM. Attach the Memory Select pin of the Z80 to one of the inputs on both of the OR gates (pin 1 and 4). Attach the previously mentioned inverter's output to the remaining input on the RAM's OR gate (pin 2) and Address 15 of the Z80 to the final remaining pin on the ROM's OR gate (pin 5).

What you have now is a circuit that will enable either the RAM or ROM when the Z80 wants to address memory space, not I/O space.

Why an OR gate? Because all of the signals in question are negative logic, meaning that when the CPU or memory or whatever makes/sees the signal as a binary 1 it is at ground potential, not +5v. This isn't insane because it can be useful in certain conditions, which I won't go into here. De Morgan's law is something like an an OR gate can be made a AND gate if the inputs and the output are inverted. Because we want to AND together the Memory Select signal and the Chip Select signal (Memory AND the chip must be selected before it's enabled) we need to use an OR gate. If we used an AND gate we would have to invert both of the inputs and the output, because of De Morgan's law.

If you want I can post you a schematic that will select I/O devices too.

Whew. Hope this gives you something to work with.

Thrashbarg.

EDIT: I didn't actually answer your question. RAM is 62C256 (or a similar prefix, make sure you get static parallel RAM) and the ROM's I use are 28C256.

UncleBinary
December 7th, 2006, 06:18 PM
Yeah I would try that circuit but since i want it as compact and as easy to make due to fact I never made a computer before I want to keep the keep count to a low even if it means sacrificing some memory.I really want the chip count to be 5 or 6.In todays world finding a SRAM chip that is speed compatible with 4Mhz at 4 clock cycles per opcode fetch is hard.I haven't found a SRAM chip under 500 ns.

UncleBinary
December 7th, 2006, 06:22 PM
Yeah I would try that circuit but since i want it as compact and as easy to make due to fact I never made a computer before I want to keep the keep count to a low even if it means sacrificing some memory.I really want the chip count to be 5 or 6.In today's world finding a SRAM chip that is speed compatible with 4Mhz at 4 clock cycles per opcode fetch is hard.I haven't found a SRAM chip under 500 ns so thats why I would fanthom a computer hard to without making the whoe computer memory and all out of transistors and I dont have the money for that or the time.

Does anyone know of a way to interface like a 100-300 ns SRAM on a z80a? www.z80.com only uses old SRAM chips which are hard to find now-a-days.Oh ya i forgot i got the equation wrong.I believe it is 1/(1/1 billion*nscycletime).

Thrashbarg
December 8th, 2006, 11:25 AM
Just doing some calculations, at 4MHz and 4 cycles per memory cycle, you'll get 1/1MHz which is 1uS. 500nS is half of that so you should be fine with even that slow RAM. Cache RAM out of 486's is about 120nS.

BTW, in case you've got the wrong idea about RAM timings (you might have, I don't know), it's how long it takes to look up the data in the chip and put it onto the data bus. It stays on the bus indefinitely. The only issue you'll have with RAM is if it's so slow the CPU operates faster than it - i.e. the RAM can't keep up.

UncleBinary
December 8th, 2006, 03:59 PM
no I dont have the timings mixed up just the equation a little bit.Thanks i thought i need 1000ns ram instead of 250 thank you for clearing that so now i can get to designing my computer.

UncleBinary
December 8th, 2006, 04:16 PM
www.jameco.com doesnt seem to have anything over 1k 250ns and up SRAM so do you reccomend another site?Is it possible and practical to directly connect a 200ns SRAM to a z80a during its opcode fetch?which runs at 4mhz completing a opcode every 4 clk cycles.

Thrashbarg
December 8th, 2006, 08:28 PM
Jameco sell 62256LP-12's which are 32KB 120nS devices. I think you're going the wrong way when it comes to the timings. You want them to be as small as possible so the RAM reacts to a new address quickly. Anything under 500nS will be fine, they all are anyway.

UncleBinary
December 9th, 2006, 12:45 PM
Thanks a lot.I thought you had to have the signals on for a certian time.Thanks for clearing that up for me.Does EPROM work in the same way a SRAM?Like the data on the data bus stays there indefinitly?In case you don't know my age it is 13 and yes i DONT have the following 1 common sense 2 ability to pick up even easy hints 3 a car to get the parts I need.Yes i know I type like im older.

Thrashbarg
December 9th, 2006, 03:49 PM
EPROM's are just like static RAM, except they need a higher voltage to be written to, typically 12V. I recommend EEPROM's (Electrically Erasable) which are about the same price as they act almost exactly like static RAM and are therefore easy to program. If you want to write protect the ROM to prevent the CPU from accidentally corrupting your boot monitor, just attach the Write Enable pin to +5v. It's active low so this makes sure it will never be activated.

EPROM's also have a problem when it comes to erasing them, you need a special ultra violet lamp which the chip is exposed to. This is why there's a window in EPROM's. The UV radiation emitted by these lamps is dangerous and can blind you. The other option is to leave them out in the sun for a few days, probably weeks, to erase them. But if you're developing and testing software this method takes way too long.

UncleBinary
December 10th, 2006, 06:52 PM
Ok I knew the difference between EEPROM and EPROM I just forgot the E in the last post.Trying to keep the chip count low I was thinking of using SRAM dirrectly connected to the CPU and have the 28C256-25 parralel EEPROM running at 250ns attached to a PIO port.Do you think that is a good idea?Oh ya UV lamps can give you skin cancer.

Thrashbarg
December 11th, 2006, 02:01 PM
Attaching the boot ROM to a PIO is bad for three reasons, firstly the CPU can't access it directly to actually boot from, it can't actually execute code through a PIO and you'll need more chips for the PIO itself.

Attaching RAM to a PIO is equally as bad because things like stack operations will not work, plus it'll be much slower and the CPU won't be able to execute code from it.

It's much simpler to simply attach the RAM and ROM to the CPU as they were intended.

UncleBinary
December 11th, 2006, 06:32 PM
Ok.Point taken.So uh... anyway to do that what you reccomended with as least amount of chips possible?REMEMBER copmuter must be under 8 IC's so uh KISS. keep is simple stupid.If you can upload a picture of what your talking about.

UncleBinary
December 11th, 2006, 07:51 PM
How do I interface both of those without losing any memory capacity?plz include some sort of picture.

Thrashbarg
December 12th, 2006, 01:25 PM
Chip Count:

1) Z80
2) 62256 SRAM
3) 28C256 EEPROM
4) 74LS32 (memory access decoder)
5) 74LS04 (RAM/ROM decoder)
6) 74LS138 (I/O decoder)
7) 8250 UART (serial port)
8) MAX232 (TTL to RS232 voltage converter)

Looks good, though I may have missed out on one. I included the 8250 UART so you can get a serial port, you want to be able to see some output.

This is as simple as a computer can get, trying to get it under 8 chips and still maintain functionality is tricky, unless you want a traffic light controller.

There is 64K of address space on the Z80, in this basic configuration there is 32K ROM and 32K RAM which fills it. There is still room for I/O devices on the 256 byte port address space. Notice on the Z80 pinouts how there are MEMRQ and IORQ lines, these are for Memory Request and I/O Request, which means that the I/O ports are addressed separately from memory.

UncleBinary
December 12th, 2006, 05:17 PM
Thanks thrashbarg but it would be easier and less time consuming if I had a picture or at least a discription of what pin to what pin.And how does a hex inverter (the RAM/ROM decoder) become a decoder.Wouldn't be simpler just to use address pin 15 as part of the SRAM logic and attack a NOT gate to address pin 15 and attack that to EEPROM logic?Sorry im sleepy.

Thrashbarg
December 14th, 2006, 02:47 PM
A hex inverter is a NOT gate. Hex because there are 6 devices in the one package.

Here's a schematic. I didn't put in the 8250 UART because they're a pain to get going. If you program the lights to blink and they do then you know it's working and you can continue from there.

http://kaput.homeunix.org/~thrashbarg/Z80SBC.png

The crystal oscillator isn't the best but it'll do. To make sure it's working you can use a frequency counter or an oscilloscope. If you don't have one then you can use an LED. Attach the anode to pin 8 of the inverter and the cathode to ground. If it lights then we're half way there. Attach the anode to +5v and the cathode to pin 8. If it lights again then it's working. This is because when a TTL device is in a logic 1 state it's effectively attached to +5v and in a 0 state 0v. The oscillator is too fast to see the blinking but if it lights when you connect it both ways then you know it's in both states and thus oscillating.

The reset circuit works by charging the capacitor through the resistor slowly. When the voltage on the reset pin reaches the TTL threshold (I think about 4V) the CPU will come out of the reset state and start executing code at address 0000h (the ROM). When you press the reset button it discharges the capacitor and the reset pin will be in a low state until the capacitor charges again. This delay is necessary to allow enough clock cycles to get to the CPU while it's in the reset state so it resets correctly.

Any questions? ;)

UncleBinary
December 14th, 2006, 03:39 PM
I could have thought of that.I am almost done with the schematics I just have to get a UART or a USRT on it to get a graphical interfeace up and a keyboard.I'll show you when im done to see if I got it right.

UncleBinary
December 18th, 2006, 08:14 PM
Quick question before I finish the schematics.If I use a 138 decoder to interface 2 PIO's do I need a buffer or will the clock and CPU signals be sufficent?

Thrashbarg
December 19th, 2006, 03:27 PM
I've not needed to use a buffer for the '138. Just attach it to the address bus and to the /CS pins of the devices.

UncleBinary
December 20th, 2006, 10:37 AM
You dont get what im asking.When attacking the pins needed to synchronise the PIO's do they have to be buffered to split them and to to match the voltage requirements?

Thrashbarg
December 20th, 2006, 03:12 PM
You dont get what im asking.

You're right. Maybe you should ask better questions.


When attacking the pins needed to synchronise the PIO's do they have to be buffered to split them and to to match the voltage requirements?

Huh? Do you need to synchronize PIO's? Why? What voltage requirements? Be more specific.

mbbrutman
December 20th, 2006, 03:51 PM
I think thread has gone on long enough - up to seven pages now. It is reading more like somebody getting very elaborate instructions for a homework assignment.

Thashbarg has been very supportive, and I'd like to thank him for that. But let's not wear him out.

UncleBinary - hit the textbooks/datasheets again, and take it offline. Let us know when you are done and how it came out.