This is a Fram mod rather than a Sram mod that WilyKat is doing. WilyKats Mod sparked me off looking for an alternative Fram device. Thanks WilyKat for the help given. The Fram is more expensive than the Sram version but.... Unlike Sram does not need a large storage cap to hold memory. So no loss of data for years and years and years.... IC is a Cypress FM18W08. It's a Fram with a similar pinout. I have installed this in my Duo-R with the extra data line hooked to Gnd and all works OK. Formated Ram OK. Have just tried Soldier blade and save is in the bank. Just ordered some switches which are Hartman PT65503 16way hex. This is a rotary switch that will have pullup resistors giving an extra 16 banks of data. Will wire up the switch when it arrives and post to all a wiring diagram. This will of course work with WilyKats great piece of work on the next thread. I will probably upgrade mine to his switching circiuit when he's finished it.
Now i don't know which mod to do =[ but this, for the sake of longevity seems like the best option. Im gonna have to compare this to the sram in the turbo cd interface unit.
Here is some info of my installation. Switch has been added and all works. 1. Remove original IC and add wire to Pad 21 2. Flatten pins on new IC for wiring. Note I have used the VCC/+5v input of the original Sram cap not the output which the Sram requires. Rear pinout of switch. Hotglued switch into hole in cover. Note pullup resistors and used a cutdown 8pin IC socket for ease of removal if switch needs changing. Finished view of Ram Bank selector.
It should be noted some system uses DIP package rather than SOIC package. AFAIK TurboCD is SOIC, and it is located on the main board with the connector. TurboCD has 3 separate boards, one that handles power conversion and filtering, and one more with CD connector that goes on top. It is a pain in the butt to take it apart. The 2 I took apart, all the wires were soldered in (except for rear power jack and video jack) so you'd have 3 floppy boards and a rat nest of wires just to get to the SRAM. One of the 2 on the left side of the middle board. I'd have to dig up my original picture or take apart my CD system to get an idea exactly where. I expect the IFU-30 (PCE CD) has SOIC as well. Turbobooster Plus, Tennokoe2, and probably other external memory bank without CD are DIP based. Super CD is probably SOIC as well but it's rare enough that I will go out and make someone's life a living hell if they ruin the Super CDROM
You could use one of these. Its a 28pin dip to soic adaptor. https://www.sparkfun.com/products/496 The adaptor is wider than the IC so you may need to place wires at one end or longer pins.
The pitch width of the soic is wider than the Dip so you would have to off set the pins under the IC. I guess you could use a right angled header soldered onto surface mount pads underneath. Just longer pins on the 28pin adaptor would work too. I think the off the shelf adaptor would suffice unless your up to making some Helder?
Heres a 28pin soic to 28pin Dip 300mm. US http://www.kr4.us/soic-28-to-dip-28-smt-adapter-1-27-mm-pitch-300-mil-body.html UK http://cpc.farnell.com/1/1/202830-proto-advantage-pa0011-adaptor-soic-28-dip-28-1-27-300mm.html Just browse for a 28pin soic to 28pin Dip 300mm adaptor
So how wide is the dip package of the SRAM? Maybe have a Datasheet of it or is it the one wilykat linked to in his thread? Would be simple to make such an adapter using the SMD pads like in those links.
The original 2k SRAM used in Turbobooster Plus and Tennokoe2 is 300mil wide or about 6.2mm. Duo, Duo=R, and TurboCD used SOIC package which is about 3.9mm with pin making it about 6mm wide total. 32K SRAM and FRAM has the same width as original but that is the limit, larger capacity SRAM are wider Anyway if you want to use FRAM in SOIC package on older device that has DIP space, you will need that 300mill bottom to fit in existing holes. And you need 24 pin adapter, not 28 since the original is only 24 pins. Yo can use that 28 pin adapter PCB to go on top of the 24 pin DIP to SOIC adapter to use larger memory chip.
My plan was to do like I did with the other adapter and make it convert from 28 pin to 24 pin DIP with the extra address lines and resistors.
I quite like the idea of the resistors on the adaptor. You could also add GND to be transfered to the switch . One difference between my mod and Wilykats is that I use the +5v prior to the memory reservoir cap. It does not need to be powered when off . Maybe add a dual pad for +5v for distribution. Wilykats mod could also use this. The 300mm adaptors use surface mount pads underneath with right angled headers. It would be cheaper on your PCB to do this. No drill pads.
There is no price difference on having drills/vias or not using them. Used to be an issue, but these days its not even considered as a cost.
