HP41 Bank Switching question



#4

I am busy implementing bank switching in my MLDL2000, and that looks pretty good right now. The problem is that I am running out of space in the chosen CPLD (256 macrocells), and the next step is a much more expensive device.

AFAIK the HEPAX module is the only one using all 4 banks in a page. Is there any knowledge of other modules supporting more than 2 pages? I could than make an exception for HEPAX and have 4 banks in one particular page, while all other pages support 2 banks. A limitation would be that HEPAX would work in one particular page. Would this be a problem for any intended users of the MLDL2000?

A more general note: Bank Switching is the last features that I need to fully test in the design. I am busy prototyping and all looks well. Will start working on the final PCB layout soon.

Meindert


#5

Meindert,

I know of no other module or device using more than 2 banks. The HEPAX appears to have been the sole exception in this, as with a few other aspects more (it broke many 41-world barriers).

I see no issues with having it at a fixed address, as long as it still only uses one page.

In fact, "all the others" probably amounts to just one (the Advantage ROM), or how could your MLDL deal with the IR_Printer module and the CX_Functions??

Maybe I'm missing some bank-switched ROMS; after all Zengrange implemented support for bank-switched into their Zeproms, but I'm not aware of anybody who actually used such functionality.

Best,
ÁM.


#6

The W&W RAMBox II (64k) seems to use a non standard bank switching scheme. It uses the ENBANK 1 to 3 opcodes to switch pages between the two 32k RAMboxes. I'm working to emulate it on Emu41. More details soon ...

J-F


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