How to test memory in an HP48 RAM card

[Jonathan Busby]

(01-25-2021 12:15 AM)mfleming Wrote:  

(01-24-2021 07:04 PM)Jonathan Busby Wrote:  If the Cypress F-RAM chip had a, say, 192MHz clock instead of just 40MHz, then there'd be no problem. I've been in correspondence with a Cypress Semiconductor engineer, so we might find out if Cypress Semi is planning on releasing faster chips any time soon.

I've looked at a number of persistent memories and the fastest clock I can remember seeing was 66 MHz. See what's available in quad-SPI memory. With a higher clock rate that might get you in range, though I know of no low end microcontroller with hardware QSPI support.

Cypress Semi makes F-RAM chips that have 100 trillion ( as opposed to 1000 trillion in their device which I really want to use but may be too slow ) read / write cycles and clock speeds of 108MHz for SDR QSPI and 54MHz for DDR QSPI. The downside is that the read / write endurance is less than a factor of ten than the chip I really want to use. Also, the power consumption is higher and the highest capacity chip is only 4Mbit x8 . I guess I *could* use this if I implemented a "flash translation layer" in hardware using a low power CPLD or FPGA. I know that F-RAM isn't flash but since both wear out, the same principles and algorithms used for wear leveling in NAND flash would mostly also apply to F-RAM. I just wish that their 1000 trillion read / write endurance part was faster or supported QSPI :/ It would make things a lot easier.

Regards,

Jonathan