Changes
== AMSDOS RAM 1 (always at BE40h..BE7Fh) ==
BE40 2 Pointer to Disk Parameter Header CP/M DPH for Drive A and drive B (A910h) (CPM:AE58h) (see below) BE42 2 Pointer to Disk Parameter Block XPDB for Drive A B (A890h) (CPM:ADD8h)
BE44 2 Delay for Motor Spin-up in 1/50 seconds (0032h)
BE46 2 Delay for Motor Spin-down in 1/50 seconds (00FAh)
06h 2 DIRNUM Current Directory Number
08h 2 DIRBUF Pointer to Directory Buffer (A930h)
0Ah 2 DPB Pointer to DPB XDPB (A890h/A8D0h for Drive A/B) Drive Param Block
0Ch 2 CSV Pointer to CSA (A8A9h/A8E9h for Drive A/B) Checksums
0Eh 2 ALV Pointer to ALT (A8B9h/A8F9h for Drive A/B) Allocation Table
== Finding the XDPB for a drive ==
The 2 byte pointer at &BE40 points to a list of DPH structures, 1 per drive, listed in order.
In most AMSTRAD dos there is space for 2 only.
To get the XDPB for a drive (this works on [[VDOS]], [[X-DDOS]], [[AMSDOS]] and [[Parados]]:
;; A = drive
ld l,a
ld h,0
add hl,hl
add hl,hl
add hl,hl
add hl,hl
ld de,(&be40)
add hl,de
ld de,&A
add hl,de
ld a,(hl)
inc hl
ld h,(hl)
ld l,a
;; HL = address of XDPB
On VDOS, to access the XDPB for the 3rd drive, you need to use |S,1:|A and then read it.
On Dobbertin HD and Vortex HD you can't get the XDPB for the hard disc partitions using the above code.
[[Category:Programming]]
