This commit is contained in:
Nero 2019-10-16 21:09:31 +00:00
parent 4abfab2812
commit b3014ef8e4
3 changed files with 26 additions and 30 deletions

View File

@ -13,7 +13,7 @@ fcb_cs: equ 15 ; byte cluster size: 0=128, 1=256, 2=512, ...
fcb_co: equ 16 ; word start sector for theoretical cluster 0
; Read/Write pointer (6 bytes)
fcb_left: equ 18 ; word number of bytes left to read from diskbuf
fcb_left: equ 18 ; word number of bytes left to read in current sector
fcb_off: equ 20 ; dword offset in disk (not in file)
; Link to directory item (4 bytes)
@ -23,6 +23,7 @@ fcb_end: equ 32
fcb_open_rootdir:
mov dl, 0x01
or dl, 0x80
mov [bx], dl
dec dl
@ -30,6 +31,7 @@ fcb_open_rootdir:
; Default 2 heads, 9 sectors
mov word [bx+fcb_spt], 0x0209
xor ax, ax
xor dx, dx
lea di, [bx+fcb_ss]
; Sector & Cluster size 128 bytes
mov cx, (fcb_end - fcb_ss)
@ -39,9 +41,7 @@ fcb_open_rootdir:
call drive_read
; copy sector size
mov ax, [diskbuf + 0x0B]
; ... save as number of valid bytes in diskbuf
mov WORD [bx+fcb_left], ax
mov ax, [diskbuf + fdc_ss]
call log2
sub ax, 7
; ... save as sector size
@ -55,35 +55,17 @@ fcb_open_rootdir:
mov byte [bx+fcb_cs], al
; copy sectors per track
mov al, [diskbuf + 0x18]
mov al, [diskbuf + fdc_spt]
mov byte [bx+fcb_spt], al
; copy number of heads/sides
mov al, [diskbuf + 0x1A]
mov byte [bx+fcb_nos], al
ret
xor dx, dx
mov ax, [diskbuf + fdc_sf]
mul byte [diskbuf + fdc_fn]
add ax, [diskbuf + fdc_rsc]
int3
fcb_get_sector_mask:
push cx
xor ax, ax
not ax
mov cl, [bx+fcb_ss]
add cl, 7
shl ax, cl
pop cx
ret
fcb_getc:
push bx
call fcb_get_sector_mask
not ax
and ax, [bx+fcb_off]
xchg ax, bx
add bx, diskbuf
mov al, [bx]
pop bx
add word [bx+fcb_off], 1
adc word [bx+fcb_off+2], 0
dec word [bx+fcb_left]
ret

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@ -22,8 +22,7 @@ init:
mov dx, banner
call print_string
mov si, init_program
call exec
call exec_chain
cli
.halt:
@ -50,6 +49,7 @@ cpm_syscall:
%include "char.asm"
%include "exec.asm"
%include "fdc.asm"
%include "fcb.asm"
%include "fcbparse.asm"
%include "drive.asm"

14
lib/fdc.asm Normal file
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@ -0,0 +1,14 @@
; FDC Descriptor / BIOS parameter block
fdc_ss: equ 0x0B ; WORD sector size
fdc_sc: equ 0x0D ; BYTE sectors per cluster
fdc_rsc: equ 0x0E ; WORD reserved sectors
fdc_fn: equ 0x10 ; BYTE FAT tables
fdc_rde: equ 0x11 ; WORD root directory entries
fdc_ts: equ 0x13 ; WORD total sector count
; 0 if >65535, use lrgts then
fdc_mi: equ 0x15 ; BYTE media descriptor byte
fdc_sf: equ 0x16 ; WORD sectors per FAT
fdc_spt: equ 0x18 ; WORD sectors per track
fdc_nos: equ 0x1A ; WORD sides/heads
fdc_po: equ 0x1C ; DWORD partition offset
fdc_lrgts: equ 0x20 ; DWORD large sector count