FRAM71B

[Hans Brueggemann]

Some clarifications on the FRAM71B status and feature set, based on Sylvain's questions from another thread:

(01-02-2016 08:07 AM)Hans Brueggemann Wrote:  1) The oscillator is gone. FRAM71B won't have built-in UART support.
2) 8 KB chips are no longer supported.
3) 16 KB chips are restricted to BOT_FRAM and LCIM use only.
4) CN2:1 jumper now only swaps areas F_0x0..F_0x2 instead of swapping between entire TOP and BOT FRAM.
5) FRAM71B will be available as FRAM71B-512 version only.

so far for the "bad" news, and here are the good ones:
6) Bankswitching of 32KB chips between TOP_ and BOT_FRAM is now available under software control via config word in H_0x2C000.

in case you wondered why there is still the TOP_ and BOT_FRAM terminology:
7) A separate 512 KB memory module will be available to upgrade FRAM71B-512 to FRAM71B-1024 without any further HW modifications.

as for 2),3): the 8KB chips had to go because i needed the associated config bit for other purposes. same holds for the new and previously not existing limitation of 16KB chips only being available on the BOT_FRAM. see attached FRAM71B's configuration table for detatils on how the configuration bits are used.
   

as for 4): Sylvain says:

Quote:It makes sense for me that page 0 & 1 to be controlled with the CN2:1 jumper but why include page 2 with it ?
If I change the OS version with the Jumper, I do not necessarily want to change my FRAM71 config with it.

that is exactly the configuration that you would be using most of the time. so, for this use-case you would duplicate the BOT_FRAM config into the TOP_FRAM, and you should be all set.
however... consider the case where you hold the DIAG ROM in TOP_FRAM. you may now set the TOP_FRAM config differently. and by setting that config to all zero, you are now able to test "real" modules with the DIAG ROM, without destroying any of the FRAM contents. well, that's at least how it is supposed to work ;o)
the modified CN2:1 functionality still preserves the option to set up the HP-71B with some kind of "dual personality", but also allows you to quickly alter the base setup of the calculator for intermediate other purposes.