byron's stuff: selected assembler interrupts

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here's some of my favourite x86 assembler interrupts. i hope that you enjoy these as much as i do.

read light pen position
int 10h service 4

input

AH = 4

output

AH = 0

ligth pen switch not down

AH = 1

DH, DL = row, column of light pen position
CH = raster line (vertical) 0 - 199
BX = pixel column (horizontal) 0 - 319, 639

park heads ps/2 only
int 13h service 19h

input

DL = drive number

output

carry = 0

success

carry = 1

error : AH = error code

cassette i/o
int 15h

input

AH = 0

turn cassette moror on

AH = 1

turn cassette moror off

AH = 2

read one or more 256 byte blocks.
store data at ES:BX CX = count of bytes to read

AH = 3

write one or more 256 byte blocks from ES:BX count of bytes to write in CX

output

DX = number of bytes actually read. carry flag set if error
carry = 1

AH = 1 : crc error
AH = 2 : data transitions lost
AH = 4 : no data found

resident basic
int 18h

this interrupt starts up rom-resident basic in the pc