base:detect_cpu_type
; --------------------------------------------------------------------------- ; Subroutine to detect an 816. Returns ; ; - carry clear and 0 in A for a NMOS 6502 CPU ; - carry set and 1 in A for CMOS 6502 CPUs ; - carry set and 2 in A for a 65816 ; ; This function uses a $1A opcode which is a INA on the 816 and C02, and ; ignored (interpreted as a NOP) on a NMOS 6502. Detection of the 65816 is ; done by the xba instruction which is a NOP on the 65C02s. 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: rts
Ullrich von Bassewitz uz@musoftware.de
base/detect_cpu_type.txt · Last modified: 2015-04-17 04:31 by 127.0.0.1