On the search for SRAM chips for the Z80.

[makerimages]

Hi, i have a vintage HM6116L-70 SRAM chip on my hands, the datasheet and pinouts of which I know, I have also tested the chip and it works. Now, I will be ordering a Z80 amongst other things within a few weeks time. Now, the Z80 has address lines A0-A15, the HM6116L-70 has address lines a0-a10, causing some space to get lost when I`d hook that up, What I would really like to do is have 2 SRAM chips with a0-a7 so I could have 2 memory banks(later on I would have to switch one for a EEPROM).

Could you guys suggest any SRAMS that are made currently and can be used with the Z80 in the abovementioned way ^, meaning the chips have the standard RD and WR pins and a CS(chip select) pin. Prefferably the chips could be cheap.

All the best,
Makerimages

[PA0PBZ]

What I would really like to do is have 2 SRAM chips with a0-a7 ...

You are not going to store a lot of data in 2 * 256 bytes...

[grumpydoc]

What I would really like to do is have 2 SRAM chips with a0-a7

What you really need to do though is look up how Z80 addressing works.

I posted some circuit ideas not all that long ago for interfacing Z80's to various kinds of memory and there's loads of stuff on the 'net.

[free_electron]

aiaiai. no clue how to make an address decoder.

if you get two of those 6116 you wrire them up in parallel. you use the top three address lines of the z80 to drive something like a 74138 and tie outout 0 of the 74138 to CE of ram 1 , output 1  of the 74138 to CE of ram 2 and so on.
that is how you make an address decode to split out across rams.

[makerimages]

The thing is, the 6116 is not sold anymore(atleast here).

By the looks of it, id need 2 SRAMs with the same amount of address lines as the z80(a0-a15) and wire those both to the address pins, then I could use memreq of the Z80 nand'ed with, lets say a15 of the z80 to index the chip I want. Could I?

[homebrew]

Just use 62256 SRAMS (32Kx8 5V). They are available in DIP-Packages. And depending on your application one might well be enough ...
They should also be quite easy to obtain.

[netdudeuk]

I've just bought one of these

http://www.ebay.com/itm/Alliance-Memory-Sram-1Mb-2-7V-5-5V-128Kx8-Pdip32-As6C1008-55Pcn-/121112507675?

For something simple, use as many lower order address lines as you need (for example, to get 32K) and fasten the others to ground.  Or you could implement bank switching, etc.

[grumpydoc]

Did you bother to look at https://www.eevblog.com/forum/beginners/z80-single-board-memory-bank-switching/. I posted several circuits for interfacing Z80 to RAM & EPROM including using a 74LS138 to generate chip select signals for 8k devices (as per free_electron's post) and larger devices such as 2 32k chips and a design for 64k RAM bank switched with 32k ROM

All pretty simple and exactly what you're looking for.

[JoeO]

The thing is, the 6116 is not sold anymore(atleast here).

By the looks of it, id need 2 SRAMs with the same amount of address lines as the z80(a0-a15) and wire those both to the address pins, then I could use memreq of the Z80 nand'ed with, lets say a15 of the z80 to index the chip I want. Could I?

Where is "here"?

[codeboy2k]

I have a bunch of W24257AK-20 and HY658256S-20 .  These are pin compatible PDIP28 skinny , 32K x 8bits SRAM, 20ns

They have OE/ CS/ WE/ , bidirectional I/O pins, and address lines.

You should be able to interface to a Z80.

I'll mail one to you for $5.00 shipping included.

[codeboy2k]

Where is "here"?

yes, where is here... I (perhaps wrongly) assumed USA, but sometimes , even mailing a small chip in a small bubble mailer internationally is prohibitively expensive, for the sender and the receiver  too.

[iceisfun]

I have a bunch of W24257AK-20 and HY658256S-20 .  These are pin compatible PDIP28 skinny , 32K x 8bits SRAM, 20ns

They have OE/ CS/ WE/ , bidirectional I/O pins, and address lines.

You should be able to interface to a Z80.

I'll mail one to you for $5.00 shipping included.

I'm interested in one of these for a Z80 project

[codeboy2k]

I have a bunch of W24257AK-20 and HY658256S-20 .  These are pin compatible PDIP28 skinny , 32K x 8bits SRAM, 20ns

They have OE/ CS/ WE/ , bidirectional I/O pins, and address lines.

You should be able to interface to a Z80.

I'll mail one to you for $5.00 shipping included.

I'm interested in one of these for a Z80 project

send me a PM.
Cheers!

[westfw]

Well, there's this 128k*8 chip: http://www.digikey.com/product-detail/en/AS6C1008-55PCN/1450-1017-ND/4234576

That's more than the z80 can address, but ... you don't need to use ALL of it, and ... About $2 !

(The same manufacturer does make 8k*8 and 32k*8 chips at even lower prices, but why bother?)

[netdudeuk]

Well, there's this 128k*8 chip: http://www.digikey.com/product-detail/en/AS6C1008-55PCN/1450-1017-ND/4234576

That's more than the z80 can address, but ... you don't need to use ALL of it, and ... About $2 !

(The same manufacturer does make 8k*8 and 32k*8 chips at even lower prices, but why bother?)

Yes, that's the one that I mentioned was in eBay. I was going to use the classic 8Kx8 SRAMs and then came across the biggie.  Not really any point in going for the old RAM for new designs.

[fluxcapacitor]

Theres a Z80 kit on ebay,it includes 128K SRAM .

http://www.ebay.com/itm/Z80-Homebrew-Microcpmputer-Kit-with-Z80-CPU-ROM-RAM-V6366-Video-IC-SN76489-/121195367061?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item1c37ce8a95

[makerimages]

Well, all of the above ideas used a demux chip, I was more thinking of hooking something like this up to the z80 and memories(HiCS and LoCS on C4  and C3 being the CS lines for program memory and RAM).

[makerimages]

Hmm, I looked up a 62256 datasheet, and it uses One pin for the WE and RD , if it is low, it is writing, if hihgh, then reading.. but the Z80 outputs separate, actibve low WR and RD... how would I go about those?

[grumpydoc]

Hmm, I looked up a 62256 datasheet, and it uses One pin for the WE and RD , if it is low, it is writing, if hihgh, then reading.. but the Z80 outputs separate, actibve low WR and RD... how would I go about those?

Lemme see - oh yes, every single one of the diagrams I posted in the thread I referred you to showed you how to connect RD and WR.

[makerimages]

Hmm, I looked up a 62256 datasheet, and it uses One pin for the WE and RD , if it is low, it is writing, if hihgh, then reading.. but the Z80 outputs separate, actibve low WR and RD... how would I go about those?

Lemme see - oh yes, every single one of the diagrams I posted in the thread I referred you to showed you how to connect RD and WR.

Using a DEMUX I plan on using a 74LS00 NAND but, wait... I just connect OE of  the 62256 to RD of the z80 and th WE to WR?! Wow, thats easy.

I did have alook at that thread late yesterday night, on a 4.7 inch device.. So I might have missed a bit on those schematics, will have a thorough read sometime soon.

[codeboy2k]

What the hell kind of schematic is that 7400 box you have drawn, anyways???

I have been using the 7400 series since the early '70s   I think I know almost every pinout by  heart, but even I don't draw schematics like the boxes you have drawn.   You should have drawn 4 individual gates, so you can see the logic flow. ... even the box you have drawn has all the net names as if they were inputs... as if that box has 12 inputs, when I know a 7400 IC has 4 gates, 8 pins are inputs, 4 pins are outputs.

Sheesh.. why don't they teach schematics in school these days???

And while I am ranting, I wish people would stop using named nets like that, they are not for making invisible wires on your schematics.

[makerimages]

Well, bare in mind that I am just getting started with Eagle and made that part myself for convenience. How would you do it?

[fluxcapacitor]

Theres a Z80 kit on ebay,it includes 128K SRAM .

http://www.ebay.com/itm/Z80-Homebrew-Microcpmputer-Kit-with-Z80-CPU-ROM-RAM-V6366-Video-IC-SN76489-/121195367061?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item1c37ce8a95

I don't want to appear pedantic (not that that will stop me  ) but that is a collection of parts that the seller deems "Ideal for designing a simple Z80 homebrew computer". It doesn't seem to include the actual design.

I like what this fellow has done. I have ambitions to build one similar myself.
http://searle.hostei.com/grant/z80/SimpleZ80.html

Yes i know its a collection of parts,it includes a Z80.The OP said he hasn`t bought one yet .

[free_electron]

One thing I have noticed on schematics is that assigning a name label on a wire is commonly done for two reasons.
1. They connect to a wire on another sheet or one other place a long way off. So that drawing a line across the diagram would on balance not add to clarity.
2. To document a significant functional signal. A signal derived by some logic combination of various other signals. Such as may occur when mating say a Z80 to a 6800 series peripheral chip or creating a S100 bus. Neither having been designed to mate to a Z80 it is necessary to combine Z80 i/o pins to create the required read/write signal protocols to interface to them.

close but not complete.

a signal leaving a page and connecting to another page uses a PORT or a POWER OBJECT. a stub of wire with a netname on it is a big no-no for that purpose !
A netname is injected on signals that go multipoint. you NEVER use a netname to connect only two points together. thats what wires are for.

signals that go multipoint are grouped in busses. the busses are drawn as fat lines showing what goes where.

[makerimages]

But hey, the schematic would work-right?