How to check an NVRAM FM16W08? - Page 1
Forum section: electronics / projects

author: luiHS
author_rank: Frequent Contributor
timestamp: May 22, 2020, 11:10:54 pm
content: Hi.I am using NVRAM FM16W08 on one circuit, to replace the original RAM. The question is that it is giving me problems, and I no longer know if it is because they arrive defective from China, damaged when welding them (although this would be rare because I solder them in the oven, with a controlled temperature curve reaching a maximum of 237 degrees Celsius during 10 seconds, according to the datasheet it would support up to 260 degrees centigrade for 10 seconds) or for another problem of my design.I would like to be able to check these NVRAMs before installing them in my circuit to make sure that they are not really defective from the Chinese, or that they are being damaged in the circuit for some unknown reason.The question is whether I could use the TL866 II Plus programmer, selecting SRAM 6264 to check the NVRAM FM16W08. The pinout is the same, data bus, addresses and control lines, except for a second CE pin that is only on 6264 (CE # and CE2). In NVRAM there is only one negative logic CE, which matches the same pin on 6264. Both can be powered at 5v. Another more complex system would be creating my own tester for NVRAM, using a microcontroller.Has anyone used the TL866 II plus to check NVRAM or do you think it is possible to check NVRAM FM16W08 by selecting RAM 6264?, both are 64 Kbit, 8kx8, parallel, 5v supply, same pinout except a second CE in 6264 RAM.I don't have NVRAM to do the tests now, the ones I had I soldered them all on 15 boards. I'm waiting for two units to arrive in a few days, this time I ordered them from Farnell. Since they are SOIC28, I also have a SOIC28 to DIP28 adapter to put it in the TL866 programmer.Regards

author: WattsThat
author_rank: Frequent Contributor
timestamp: May 22, 2020, 11:51:12 pm
content: QuoteTrue, but F-ram is not always drop-in compatible with static ram because the address logic is different. On the FM18W18, the CE/ pin must go high between address changes since this latches the address into the unit. The static ram part does not require this behavior. Have a look at the CE state logic on page 5, figure 2 of the Cypress datasheet.https://www.cypress.com/file/136521/download

author: amyk
author_rank: Super Contributor
timestamp: May 22, 2020, 11:52:34 pm
content: Breadboard and some wires and LEDs should be enough to check if they're not completely dead. Beyond that, you could hook it up to an Arduino and exercise it.

author: luiHS
author_rank: Frequent Contributor
timestamp: May 23, 2020, 12:18:21 am
content: Quote from: WattsThat on May 22, 2020, 11:51:12 pmI have seen the graph you indicate from the datasheet, but the fact is that in some circuits RAM 6264 is being replaced by NVRAM FM16W08 and it works perfectly.For example, in the CPU boards of pinball machines from the 90s, which installed RAM and batteries, the RAM 6264 is replaced by an NVRAM FM16W08, the batteries are removed and everything works correctly.So I see it somewhat contradictory, in the datasheet they say that the access mode to NVRAM will be different from that of a RAM, but nevertheless when replacing a RAM with an NVRAM, everything works.

author: james_s
author_rank: Super Contributor
timestamp: May 23, 2020, 04:13:26 am
content: Quote from: WattsThat on May 22, 2020, 11:51:12 pmI have attempted to retrofit F-RAM into two different things so far and I ran into that problem both times. In one case the device was almost entirely working but the calibration routine would fail.