2 ; Ullrich von Bassewitz, 02.04.1999
4 ; unsigned char getcpu (void);
9 ; ---------------------------------------------------------------------------
10 ; Subroutine to detect an 816. Returns
12 ; - carry clear and 0 in A for a NMOS 6502 CPU
13 ; - carry set and 1 in A for a 65c02
14 ; - carry set and 2 in A for a 65816
15 ; - carry set and 3 in A for a 4510
16 ; - carry set and 4 in A for a 65sc02
17 ; - carry set and 5 in A for a 65ce02
19 ; This function uses a $1A opcode which is a INA on the 816 and ignored
20 ; (interpreted as a NOP) on a NMOS 6502. There are several CMOS versions
21 ; of the 6502, but all of them interpret unknown opcodes as NOP so this is
24 .p816 ; Enable 65816 instructions
28 inc a ; .byte $1A ; nop on nmos, inc on every cmos
32 ; This is at least a 65C02, check for a 65ce02/4510
34 .byte $42,$ea ; neg on 65ce02/4510, nop #$ea on 65c02, wdm $ea on 65816
40 lda #5 ; CPU_65CE02 constant
41 .byte $5c ; map on 4510, aug on 65ce02 (acts like 4 byte nop)
42 lda #3 ; CPU_4510 constant
51 .byte $f7,$f7 ; nop nop on 65sc02, smb7 $f7 on 65c02 and 65816
56 lda #4 ; CPU_65SC02 constant
59 ; check for 65816; after 4510, because $eb there is row (rotate word)
61 @L7: xba ; .byte $eb, put $01 in B accu
62 dec a ; .byte $3a, A=$00 if 65C02
63 xba ; .byte $eb, get $01 back if 65816
64 inc a ; .byte $1a, make $01/$02
65 @L9: ldx #0 ; Load high byte of word