mirror of
https://github.com/cc65/cc65.git
synced 2024-12-25 02:29:52 +00:00
38 lines
1.1 KiB
ArmAsm
38 lines
1.1 KiB
ArmAsm
;
|
|
; Ullrich von Bassewitz, 02.04.1999
|
|
;
|
|
; unsigned char getcpu (void);
|
|
;
|
|
|
|
.export _getcpu
|
|
|
|
; ---------------------------------------------------------------------------
|
|
; Subroutine to detect an 816. Returns
|
|
;
|
|
; - carry clear and 0 in A for a NMOS 6502 CPU
|
|
; - carry set and 1 in A for some CMOS 6502 CPU
|
|
; - carry set and 2 in A for a 65816
|
|
;
|
|
; This function uses a $1A opcode which is a INA on the 816 and ignored
|
|
; (interpreted as a NOP) on a NMOS 6502. There are several CMOS versions
|
|
; of the 6502, but all of them interpret unknown opcodes as NOP so this is
|
|
; just what we want.
|
|
|
|
.p816 ; Enable 65816 instructions
|
|
|
|
_getcpu:
|
|
lda #0
|
|
inc a ; .byte $1A
|
|
cmp #1
|
|
bcc @L9
|
|
|
|
; This is at least a 65C02, check for a 65816
|
|
|
|
xba ; .byte $eb, put $01 in B accu
|
|
dec a ; .byte $3a, A=$00 if 65C02
|
|
xba ; .byte $eb, get $01 back if 65816
|
|
inc a ; .byte $1a, make $01/$02
|
|
@L9: ldx #0 ; Load high byte of word
|
|
rts
|
|
|