Electronics > Repair
Has anyone replaced HP8591(E) SRAM by FRAM?
Greybeard:
Looks reasonable, but I can't say much about it.
I'm not a bus timing specialist and I don't know anything specific about the timing of the two OE CE signals.
Miti:
--- Quote from: Greybeard on December 25, 2024, 01:48:47 pm ---Looks reasonable, but I can't say much about it.
I'm not a bus timing specialist and I don't know anything specific about the timing of the two OE signals.
--- End quote ---
Which two OE signals?
Greybeard:
--- Quote from: Miti on December 27, 2024, 03:02:20 am ---Which two OE signals?
--- End quote ---
Sorry, I meant CE ...
Miti:
Bad news, I should have scoped the signals before going too deep down the rabbit hole. The fastest write time is 100ns while the FM22L16 access time is 110ns. See below the scope shots for LLW and LUW. Most writes are 16 bits but I've caught few 8 bits writes as you can see. We need a faster FRAM or NVRAM.
Edit: Oops, I was looking at the wrong parameters. Assuming the writing is controlled by WE , the minimum WE pulse twp for FM22L16 is 16nS, in our instrument case it is 100nS. The cycle time is between two WE pulses and it is, as guessed before, about 271.32 nS, four clocks of 14.7423MHz. Back to it.
Miti:
I have a question about the bidirectional level translators such as TXB0108. I see it has an OE pin for the LV side. Can I connect it to Vcc or does it have to be controlled? What happens with the 5V side if I tristate the memory side and the LV pins are left floating? I’m asking because the enable time Ten is 1uS and it is a killer. :palm:
Cheers,
Miti
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