I am a newbie of mc9sdp512 ucontroller. I am digging a CF file issue for my company and I had a hard time to understand some legacy asm code.
The following is the code:
tfr d,x ;file name pointer is in accd
lda 5,sp ;get drive num and operation type
What I don't understand is that after load 14 to accumulator b and call software interrupt. The file on CF card is open "magically". How it is opened I don't know. Here in the vector table, swi is defined as this:
word swiHndl ;$fff6 SWI
this is swiHndl:
xgdx ;accd = sp of current stack
jmp jOS_call ;do OS_call
jOS_call:: jmp 0 ;operating system call
Anyone can hlep me figure how the file on the CF card is opened?