B66SPEED TRAP
The task
P0 and P1 read two light gates on CH1 and CH2. A car trips P0 first, then P1.
Sample both on each tick of P3. Count from the tick after P0 first reads high.
The count ends on the first tick P1 reads high, that tick included. Set P2 to 10 times it.
Hold it until the next car. A car has gone once P0 reads low again.
The board
- Sources
- V1 5 V, V2 5 V square at 25 Hz, V3 2 V, V4 2 V square at 25 Hz, and V5 1.2 V square at 27.78 Hz
- Resistors
- R1 10 kΩ
- Capacitors
- C1 1 µF
- Probes
- CH1, CH2, and CH3
Key idea
Wait for P0 to read low first, so one car is never timed twice.
Hints
Each hint goes a step further than the one before. Open them one at a time.
Hint 1Show
Count in tens: add 10 to B on every tick until P1 reads high.
Hint 2Show
After the wait for low, A is 0: MOV B, A clears the count for free.
Solution
Reveal the Full SolutionThe complete program for SPEED TRAP. Open it only when you want the answer.
The reference program
The game's own solution. It passes every test and scores exactly par on every benchmark.
Time between two gates, counted in ticks.
u1SC-2 standard
W: IN P3
IN P0
JNZ W
MOV B, A
A1: IN P3
IN P0
JZ A1
T: IN P3
MOV A, B
ADD 10
MOV B, A
IN P1
JZ T
MOV A, B
OUT P2- CYCLES
- 310
- at par
- ENERGY
- 620
- at par
- NODES
- 1
- at par
- INSTRUCTIONS
- 15
- at par