there are four interrupts: int0, int1, int2, int3
interrupt vector at M[1000-1003]
only one interrupt is accepted and it runs to completion. ***
priority: int0 > int1 > int2 > int3
int n op x 31
23 software interrupt (not implemented yet)
reti op
x 31 24 return from interrupt
trap r1 #15 disable interrupt r1 = (0,1,2,3)
trap r1 #16 enable interrupt r1 = (0,1,2,3)
trap r1 #17 sleep and wait for interrupt
trap r1 #13 set timer0 range
trap r1 #14 set timer1 range
trap r1 #18 read port, r1 is port number
trap r1 #19 write port, r1 is port number
10 analog input (sine wave)
11 digital input (square wave)
12 random number input
13 master clock input
the number of clock since the board reset
last update 28 Jan 2017