lesson8.txt

#color 0xffc3e1fe
#coord 305 17
#title The Subframe Lessons
#title 108: DRAY Wires

#font 7px
#color 0xfffbfbbb
#coord 37 46
#section 8.1 Signal Propagation

Let's say we want this PSCN to control this ARAY.

One idea is to copy the PSCN to the ARAY with DRAY.
SPRK the PSCN. Did it work? (It shouldn't.)

We can debug this by stepping forward frame-by-frame.
Press 'f' to step forward a frame.

Observe that it takes two frames for the signal to reach the ARAY.
By the time the SPRK reaches the ARAY, its life has decreased to 2.

This problem arises because the first DRAY updates after the second DRAY.

#section 8.2 DRAY Wires

There are a number of ways to overcome this problem.

One way is to copy the SPRK downwards first, then rightwards.
This works because the first DRAY updates before the second DRAY.

A more general method is to replace the activating PSCN
(instead of the copied PSCN) in the DRAY-PSCN motif.

Again, this works because the DRAYs update in the correct order.

#section 8.3 Inverting Wires

Another type of DRAY wire is the inverting wire.

Here, we copy a PSCN onto a solid SPRK, deactivating the DRAY.
This transmits and inverts the signal at the same time.

#font 5px
#color 0xffbefcc4
#coord 410 48
#section Activity #8.1

Use stacking to make this set of
wires as compact as possible.

#space 15

#answer 150 10

#section Activity #8.2

Make this PSCN control all four ARAYs.

#space 15

#answer 150 10

#section Activity #8.3

What happens if two wires lead
to the same output?

Here are examples for both normal
and inverting wires.

#space 20

Play with them by SPRK-ing different
combinations of their inputs.

What do you observe?

#answer
These are OR and NOR gates.
We'll learn about NOR gates next lesson!
#answer