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 some CMOS 6502 CPU
14 ; - carry set and 2 in A for a 65816
16 ; This function uses a $1A opcode which is a INA on the 816 and ignored
17 ; (interpreted as a NOP) on a NMOS 6502. There are several CMOS versions
18 ; of the 6502, but all of them interpret unknown opcodes as NOP so this is
21 .p816 ; Enable 65816 instructions
29 ; This is at least a 65C02, check for a 65816
31 xba ; .byte $eb, put $01 in B accu
32 dec a ; .byte $3a, A=$00 if 65C02
33 xba ; .byte $eb, get $01 back if 65816
34 inc a ; .byte $1a, make $01/$02
35 @L9: ldx #0 ; Load high byte of word