DESC

; This is a demonstration of Peterson's algorithm for mutual exclusion,
; which can be used to prevent race conditions.
; See http://en.wikipedia.org/wiki/Peterson%27s_algorithm for details.
; M0 is "flag[0]"; M1 is "flag[1]"; M2 is "turn"; M3 is the target location

PROG 0
MOV 1, M0
MOV 1, M2
WAIT M1, 0
WAIT M2, 0

; begin c.s.
MOV M3, R0
INC R0
MOV R0, M3
; end c.s.

MOV 0, M0

PROG 1
MOV 1, M1
MOV 0, M2
WAIT M0, 0
WAIT M2, 0

; begin c.s.
MOV M3, R0
INC R0
MOV R0, M3
; end c.s.

MOV 0, M1