Instruction manual

0289 ;Subroutine to start a new line

0289 3e 0d write_newline: ld a,00dh ;ASCII carriage return character

028b cd 0c 00 call write_char

028e 3e 0a ld a,00ah ;new line (line feed) character

0290 cd 0c 00 call write_char

0293 c9 ret

0294 ;

0294 ;Subroutine to read one disk sector (256 bytes)

0294 ;Address to place data passed in HL

0294 ;LBA bits 0 to 7 passed in C, bits 8 to 15 passed in B

0294 ;LBA bits 16 to 23 passed in E

0294 disk_read:

0294 db 0f rd_status_loop_1: in a,(0fh) ;check status

0296 e6 80 and 80h ;check BSY bit

0298 c2 94 02 jp nz,rd_status_loop_1 ;loop until not busy

029b db 0f rd_status_loop_2: in a,(0fh) ;check status

029d e6 40 and 40h ;check DRDY bit

029f ca 9b 02 jp z,rd_status_loop_2 ;loop until ready

02a2 3e 01 ld a,01h ;number of sectors = 1

02a4 d3 0a out (0ah),a ;sector count register

02a6 79 ld a,c

02a7 d3 0b out (0bh),a ;lba bits 0 - 7

02a9 78 ld a,b

02aa d3 0c out (0ch),a ;lba bits 8 - 15

02ac 7b ld a,e

02ad d3 0d out (0dh),a ;lba bits 16 - 23

02af 3e e0 ld a,11100000b ;LBA mode, select drive 0

02b1 d3 0e out (0eh),a ;drive/head register

02b3 3e 20 ld a,20h ;Read sector command

02b5 d3 0f out (0fh),a

02b7 db 0f rd_wait_for_DRQ_set: in a,(0fh) ;read status

02b9 e6 08 and 08h ;DRQ bit

02bb ca b7 02 jp z,rd_wait_for_DRQ_set ;loop until bit set

02be db 0f rd_wait_for_BSY_clear: in a,(0fh)

02c0 e6 80 and 80h

02c2 c2 be 02 jp nz,rd_wait_for_BSY_clear

02c5 db 0f in a,(0fh) ;clear INTRQ

02c7 db 08 read_loop: in a,(08h) ;get data

02c9 77 ld (hl),a

02ca 23 inc hl