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.

Well, the reason I want to stick with Cypress Semiconductor F-RAM is that, AFAIK, they make F-RAM chips with the highest read / write endurance in the industry, which is 1000 trillion or one quadrillion read / write cycles. This makes it ideal for use as normal RAM on the HP48GX and HP48SX as it would be something like 100+ years before the F-RAM wore out, and, that would have to be a contrived case as one would have to continuously write or read the same memory block continuously.

Thanks for the tip regarding the higher clocked F-RAMs Do you remember which manufacturer makes them? Also, thanks for the tip on QSPI. That *may* solve the problem but I'd probably have to use an ultra low power Xilinx CPLD, Microsemi or Lattice FPGA for the serial-parallel conversion. Also, I really would prefer to stick with Cypress Semi for reasons I've already stated -- maybe there is another manufacturer who makes F-RAM chips with the same or better endurance compared to the Cypress Semi ones.

Regards,

Jonathan