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
15 ; - carry set and 3 in A for a 4510
17 ; This function uses a $1A opcode which is a INA on the 816 and ignored
18 ; (interpreted as a NOP) on a NMOS 6502. There are several CMOS versions
19 ; of the 6502, but all of them interpret unknown opcodes as NOP so this is
22 .p816 ; Enable 65816 instructions
26 inc a ; .byte $1A ; nop on nmos, inc on every cmos
30 ; This is at least a 65C02, check for a 4510
32 .byte $42,$ea ; neg on 4510, nop #$ea on 65c02, wdm $ea on 65816
36 ; check for 65816; after 4510, because $eb there is row (rotate word)
38 xba ; .byte $eb, put $01 in B accu
39 dec a ; .byte $3a, A=$00 if 65C02
40 xba ; .byte $eb, get $01 back if 65816
41 inc a ; .byte $1a, make $01/$02
42 .byte $2c ; bit instruction to skip next command
43 @L8: lda #3 ; CPU_4510 constant
44 @L9: ldx #0 ; Load high byte of word