Re assemblable version of NAS-DOS version 1.4. Created Jan 2014, Phill Harvey-Smith.
Originally disassembled Jan 2014 from the MESS nasdos.rom, which was a modified copy of nasdos 1.4.
Updated 2018-12-05 to match v1.4 ROMS dumped from PHS' Nascom 3.
To be built with z80asm : https://www.nongnu.org/z80asm/
Tracks are numbered from 0, sectors are numbered from 1. Track 0 is reserved as follows: Sector 1: Userboot (see documentation) Sector 2: Disk Id (name) Sector 3: (and remaining sectors of the track) Directory entries
80 tracks of 16 sectors of 256 bytes. Disk can be single-sided or double-sided. A double-sided disk is treated like 2, independent single-sided disks: Each side has its own Userboot, Id, directory etc. A file cannot span from one side to the other. The two sides are associated with even/odd drive numbers.
A disk image for a 2-sided disk will be 80162562 = 655360 bytes The first 16256 bytes will be sectors 1-16 of track 0, side 0 The second 16256 bytes will be sectors 1-16 of track 0, side 1 The third 16256 bytes will be sectors 1-16 of track 1, side 0 (etc).
"NASCOM FLOPPY DISK CONTROLLER HARDWARE MANUAL" "NASCOM DISK OPERATING SYSTEM NAS-DOS1"
https://80bus.co.uk.mirror.jloh.de/pages/nascom/documentation/Nascom_FDC_Controller.pdf http://www.nascomhomepage.com/pdf/Nasdos.pdf
The file nasdos_sd.asm (which includes sd_sub1.asm, sd_sub2.asm and sd_sub_defs.asm) is modified source to use Neal Crook's "nascom SDcard" (connected to the NASCOM PIO) instead of a floppy disk controller. See https://github.com/nealcrook/nascom/tree/master/sdcard