HP-48 FRAM Cards

[Dave Frederickson]

(07-23-2016 01:04 AM)snrowe Wrote:  

(07-23-2016 12:58 AM)JDW Wrote:  JDW says, "You're welcome." :-)



The only thing that PDF educated me on was temperature. So we shouldn't keep FRAM cards in a room higher than 85°C. That's good to know. As the mercury rises above 80°C, I think I'll switch on the A/C. :-)

Seriously, I don't see the negative you are mentioning. The data shows FRAM to have greater endurance than Flash, and most computers use SSDs now. So in effect, you're safer using FRAM in a 48GX than a computer is using its SSD! How is that a knock against FRAM in a 48GX?

Quote from article on page 3:
"A read operation in a FRAM is destructive because it requires switching the polarization state in order to sense its state. The read operation has to restore the polarization to its original state after the initial read which adds cycle time to the read operation."

Also page 6 the table states FRAM has a destructive read.

I see, in this case, "destructive read" has two different meanings. Magnetic core memory and FRAM employ a destructive read architecture where it's necessary to change the state of a bit in order to read the value. The original value then needed to be rewritten back. This is destructive in that the data is lost when read, but does not wear out the device. Core memory had no such characteristic. With respect to endurance, reading and writing reduces the lifetime of FRAM and flash, so one could say that FRAM is more destructive than flash because of the write-after-read architecture, but FRAM still has much better endurance. Does that help?

Just to clarify things a little more, it's not necessary to change the state of all the bits in order to read them. With core memory, and forgive me if I get the polarity incorrect as it's been a while, to read the data all ones are written to a register. A sense line then detects a pulse from the bits which were zeros and changed state. Then the zeros are written back.

Dave