HP-41 and Hepax Filesystem

[Ángel Martin]

(02-06-2020 12:14 AM)pablo2000 Wrote:  Hi folks

Does anyone here either know, or know where to find something documenting or detailing the ins and outs of the Hepax filesystem? The standard Hepax manuals offer a few tantalising hints before stopping short with a statement that “the filesystem works by magic and voodoo and you should pay no attention to the man behind the curtain and let us take care of everything for you.” Or something like that.

Check the description of HEPINI in page #34 in the PowerCL_Extreme Manual posted at:
http://systemyde.com/hp41/documents.html

Code:

Address Byte value                  Comment
x000    ROM id# => not same as pg#   Always done
xFE7    Previous HRAM page#         (zero if 1st.) Always done
xFE8    Next HRAM page#             (zero if last) Always done
xFE9    Fixed value = 091           Won’t be overwritten if not zero
xFED    Fixed value = 090           Done always
xFEF    Fixed value = 091           Won’t be overwritten if not zero
xFF1    Fixed value = 0E5           Done always
xFF2    Fixed value = 00F           Done always
XFF3    Fixed value = 200 (or 100)  Done always

"Two of the byte values shown in the table above located at addresses 0xpFE9 and 0xpFEF have a different treatment: they will be branded only if the previous content is zero. They denote the initial address in the page where the next file or program will be written using HSAVEP, HCRFLAS and HCRFLD. Their values will vary as more programs or content is written to the HRAM page, thus should not be overwritten by HEPINI – or else the HEPAX FileSys catalog will become corrupt."

HTH,
ÁM