Internal 32K mod (Tursi) and 32K SD RAM Chip....

[repetto74]

Hi Guys,

 

I am willing to perform the 32K internal mod as per the Tursi tutorial. I have a 32k SDRAM labelled HY62CT081ED70C and I was wondering if this one is pin compatible with the CY7C199 ? (they are both DIL 28 of course but the CY7C199 is shorter in width).

 

Thanks

Rick

 

[jedimatt42]

Oh, I hate it when I compose a thoughtful response with links and information and stuff, and then it just goes away because of the editor...

 

---

 

Here's the short version. The Hyundai/hynix chip, it is hard to find the exact datasheet for it. You can find some close cousins.

The close cousins have compatible characteristics to the cypress chip you mentioned. Close enough that I'd just go for it.

 

Ideally though, you want the datasheet so you can learn things like decoupling needs, and stuff...

 

both chips seem to be 5v friendly cmos. And have all the data and address lines grouped to the same pins. And the OE, WE, CS, VCC, and VSS are all on the same pins.

 

I'd guess from your part number, that it is a 70ns chip, which should be plenty fast.

 

That is all based on the cousin's datasheet.

 

Good luck!

 

[email protected]

[repetto74]

Hi Jedimatt,

 

Ok thanks a lot :-). Yes I think I may try using this SDRAM and see the result. Anyway the mod requires a lot of wiring so if not working it would be just a matter of removing the piggybacked SDRAM and replace it with a Cypress one.

 

My soldering iron is heating.....

[+Ksarul]

Here's a Hynix datasheet that probably covers you. . .and if you look later in the datasheet--the chip markings actually omit the first 08 after the CT, so it is the right datasheet.

Hynix HY62CT08081E Series 32K x 8 Datasheet.pdf

Edited December 23, 2017 by Ksarul

[GDMike]

Can you expand on that to make a "FULL" 1MB RAM source internally? Id buy one! BUT I don't want to change ANY of the hardware internally, "DEFACING". AND IF there was a way to do a Serial MEMORY access read/write and make it available thru a serial port (data bus console side) that would be cool and IF it wasn't too much to ask, Adding a Serial Port Extension to allow "FLASH DRIVE" Swap outs Preferably through Cartridge port. - up to 64GB access for storage. ..might as well add Nic card via tcp for TCP\IP connections (telnet).

hmm, can you get right on that please..

[repetto74]

Hi Ksarul,

 

Thanks for the datasheet :-) Good to have this one also

[repetto74]

So a close look to the two datasheets will give some differences with the address lines which have different pinouts positions. I will have to pay attention to this when doing the wirings.

 

 

 

 

Hynix SDRAM 32K Datasheet.pdf

[jedimatt42]

Since it being used as ram with a single microprocessor, the order of address lines is is non-consequential. It does not matter if A0 and A5 are swapped. In fact it can make wiring easier. Same for the data lines... It is ok for D3 and D7 to be swapped.. it is only messy if you want to put a logic analyzer on there.

 

[email protected]

[repetto74]

Hi Jeddimatt42,

 

So that means I can do the wirings according to the tutorial pinouts and consider I am wiring a CY7C199 i/O the Hynix SDRAM ?

Edited January 2, 2018 by repetto74

[jedimatt42]

( this forum drives me nuts!!!! every other post fails... )

 

-- again...

 

Yes, I believe I checked at the beginning of this thread, that the WE, OE, CS, VPP, and GND all have the same pin location and quality ( active low or not )... And that the address lines are grouped the same, and the data lines are grouped the same. So you should be good to go!

 

[email protected]

[repetto74]

Hi Jedimatt42

 

Thanks for your advice :-). Sorry If I ask but despite the fact I do have soldering skills I am really a noob concerning IC's architecture and how they work :-).

[jedimatt42]

I was asking these same questions a couple years ago..

 

[email protected]

[repetto74]

OK so done and at first try with SIZE command I do have 24488 bytes free for programs :-). I think it is good

[jedimatt42]

Congrats!

 

https://github.com/jedimatt42/ti994a-32kmemtest/releases

 

There is a memory test program there you can use, I would usually let it go for about an hour on each of the sideport 32k cards I built.

 

It might expose a cold joint on a address line or something... sadly, it won't help you find which if any is bad...

 

Fred Kaal also has some memory tests on his site: ti99-geek.nl with some good explanation of how certain tests can lead you to isolating a tiny short, or weak connection.

 

But... hopefully my test will just pass for you!

 

I don't believe XB did any testing beyond a few bytes to check if they are mutable.

 

[email protected]

[repetto74]

Hi Jedimatt42,

 

Thanks for the test I will let it run as soon as possible :-). Actually all wiring shave been checked for continuity at their solder joint with a multimeter and all was good

[repetto74]

OK so I mounted back the PCB into its metal case and mounted back the machine. On power up I was getting a garbled prompt screen with weird colors. After re-opening and testing all was fine again so I do have probably one or more shorts with the metal case. I suspect probably the piggybacked LS021 to have its legs touching the metal case. I will try to tape the whole area and check again

Edited January 5, 2018 by repetto74

[repetto74]

And test PASSED!

[JamesD]

And test PASSED!

Congrats! I've wanted to make that mod myself.

 

By any chance do you have an iPhone? Just my first thought every time I see a landscape photo with portrait orientation.

 

[repetto74]

Hum hum....... yes I do have an Iphone Don't ask me why they are displayed 90 degres it's a mistery for ma also

[Omega-TI]

Hum hum....... yes I do have an Iphone Don't ask me why they are displayed 90 degres it's a mistery for ma also

 

Fixed!

[+arcadeshopper]

Hum hum....... yes I do have an Iphone Don't ask me why they are displayed 90 degres it's a mistery for ma also

 

its because you didn't wait for the iphone to figure out orientation before taking the picture, phone cameras orient the picture based on the accellerometer/compass and sometimes it takes a sec to "sync" to the right direction

[repetto74]

Hi Arcadeshopper,

 

Thanks for the explanation