FRAM NVRAM Board

[hoopstar]

Following

[Gareth]

Ditto

[jenko]

Have been looking into the fm18w08
the 28 pin dip package has same pinouts voltage and temp specs as ds1245y however the read and write pins require high vs low to enable.
Hope I have this correct I am not an electronics expert
so are we talking an adapter board with a logic gate on it
which would probably package smaller than the ds1245y ?

[antus]

Im at the clipsal 500 this weekend so I likely wont have time to look at this for a bit, but there are some points:

1) be sure to compare the DS1245Y-75IND to get the industrial temperate and power spec ratings more suitable for automotive
2) if the write logic is inverted then yes it would need to be inverted on the pcb which shouldnt be hard
3) the current update path (unannounced until now) is courtesy of festy who has designed a lithium battery powered nvram module which is pin compatible with existing boards and is a drop in replacement. This has not yet been tested or built but is the current plan for when DS1245s go end of life or become prohibitively expensive.

dsfesty.png (28.57 KiB) Viewed 4919 times

4) we would need to consider how to populate it initially. We would need to check burner compatibility and the possibility of programming it as a DS1245Y after an ID check failure or mismatch.
5) it could be a good time to consider direct usb connectivity to the module to flash it from pc over usb but this is a lot more complex and therefor expensive and we may also run in to space problems. If the extra cost is more than a burner then it becomes questionable if its worth it. Also people with more than one board probably wouldnt want to pay extra for every board and would rather use the same burner they already have. Thoughts?

[BennVenn]

I spent the morning (37deg!) at the wreckers to pull a few ECU's and memcals out of a couple of pulsars. Also got a complete sensor set and loom so I can bench it. Now, all they had were TBI but in the back of one of them were two extra ecu's from 1.8 port injection. I currently have the TBI in my beetle so all the hard work is done mechanically though I find it odd that the TBI is a low impedance injector while the Port injected are all high impedance. From an ECU viewpoint it wont make much difference as 1.8ohm TBI is more or less the same as 4 x 12ohm injectors paralleled. What does make a difference is driving the TBI injector with no current limiting. I've cooked an injector previously by doing just this. I'll pull the ECU's apart today and look at the injector drivers.

I'll be sure to source industrial/mil spec FRAM. I'll be adding a lot of supply decoupling and filtering.

The 18W08's control lines are all active low, which is common to all conventional SRAM/(E)EPROM/Flash etc... I don't see a problem here.

I'll either be adding a micro to flash the chip on board, or building a dedicated memcal dumper/flasher. I've already got these boards made up from another project, parts count to be around $9. I can easily integrate it but there is no need. You rarely need to re-write unless something goes terribly wrong. Plus I would like the ability to go to the wreckers and dump all the memcal's I can get my hands on, just out of curiosity.

All up parts price for both the memcal and flasher is under $20.

32k FRAM's are cheap, 64k/128k IC's don't follow the price trend so it looks like there will be more than 1 FRAM IC onboard unless people are happy paying a premium. There is more than enough real estate to house 128k+

And finally, I really REALLY like the dual battery backed SRAM board. These batteries reliably last 10yrs+ and having two means replacing without data loss. I have a few 8mbit SRAM IC's in tsop package on my desk, these cost about the same as a 128k FRAM IC. But you still have the battery as a point of failure.

One last thing, there is no air temp sensor on the TBI system. No plug in the Loom. Interesting!

[jenko]

The FM28V020 is supposed to be a sram drop in replacement .
specs here http://www.cypress.com/file/136591/download.
would that be more suitable

[BennVenn]

except that is a 2-3.3v part... Too much effort in level converters, bus multiplexers etc...

The drop-in side of things isn't too important if I'm getting a new set of boards made up. Now I have a memcal in my hand I can get the dual-row header pinout identified and start cading up the new board.

I read the netres was a laser cut resistor matrix. My memcals all have 14pin dip IC's - I'm guessing they're resistor packs? If this is common in other models, there is no need for a pass-through to the original memcal? Or is there knock filtering on these more advanced memcals?

On to the memcal dumper/flasher. I'll post up my 3 pulsar memcal bins soon, I have my VP ecu coming in the mail this week.

[antus]

All the netres specs are known and most bins are available too. Have a look at the FAQ (top right) im fairly sure there is a link to details there.

[BennVenn]

Dumping those EPROM's had me scratching my head! Why would they make the lower 16kbytes high impedance on the bus?!?!? Unless A14 is an inverted CE line. I'll need to look into that a bit more. Edit: It's a 16k ROM! A14 is actually a /PGM line.

I've dumped all 3 memcals and there are differences between my dumps and those over in the 4cylinder dump page. Bytes 2,3,4 and 5 are different on my ROM's to those uploaded here, on all 3 ROM's. The remaining 16kbytes are identical. Repeated dumps show the same thing, over and over so I'm fairly confident it's not a hardware bug on my end. Again, I'll need to look into that more. Edit: Looking through the .ecu file, seems those values are the production sequence number.

Can someone point me to an XDF file for the $54 bins? Edit: Found it!

Next is building a board to house the FRAM and testing!

[Dylan]

I'm of no help to you but I love your work and enthusiasm please keep it up.
All your questions can be answered on here. Please don't lose interest.