43 lines
1.0 KiB
ArmAsm
43 lines
1.0 KiB
ArmAsm
|
|
|
|
vector_real:
|
|
|
|
// Use MEMUSS as temporary storage location - checked on real C64 that this is the
|
|
// address originally used; after calling VECTOR and checking zero page
|
|
// area afterwards, the address could be found there
|
|
|
|
// According to 'Compute's Mapping the Commodore 64' page 237,
|
|
// the CBM implementation does not disable IRQs - yet, the
|
|
// 'C64 Programmers Reference Guide' does not contain such
|
|
// warning and does not mention any preparations needed.
|
|
|
|
// Initial idea was to do php, cli, ..., plp to make the routine safer,
|
|
// but it seems it might cause problem with initialization on XEMU emulator
|
|
// XXX find out, why
|
|
|
|
// Prepare the user data pointer - strange order to reduce risk
|
|
// of potential similarity to the original routine
|
|
sty MEMUSS + 1
|
|
stx MEMUSS + 0
|
|
|
|
// Select routine variant - store or restore vectors
|
|
ldy #$1F
|
|
bcc vector_restore
|
|
|
|
lda CINV, y
|
|
sta (MEMUSS), y
|
|
|
|
bcs vector_end_loop // branch always
|
|
|
|
vector_restore:
|
|
lda (MEMUSS), y
|
|
sta CINV, y
|
|
|
|
// FALLTROUGH
|
|
|
|
vector_end_loop:
|
|
dey
|
|
bpl vector_restore
|
|
|
|
rts
|