Now the software, a table driven loop with nothing specific to a
traffic light application, Each byte of the table is used as follows:
| BIT | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
| USE | R | Y | G | <-delay-> |
Where R Y and G are the outputs to the LED drivers (1=on), and the
lower 5 bits hold the number of seconds (approx) that the output is
maintained for. The special code 00 denotes the end of list and causes
the table pointer to be reset to the start, The program is relocatable
and will run on NAS-SYS or T1 to T4 monitors, execute at E00:
Keyboard Bits
I was surprised to see in
INMC80 1
that Martin Dyer was using the
PIO
and push button switches for the controls on a
space invaders
game.
The NASCOM keyboard is suitable for this job, providing the correct
software is used to read it. The KBD routine does give information
about keys that are held pressed, as anyone with a repeat keyboard will
confirm. Whenever the routine is called it updates the bit map, KMAP
from C01 to C09, where each bit in the map represents a key on the
keyboard (1=pressed), Here’s a short program to tell you the byte and
bit in KMAP for any one key as it is pressed, The program should run
on NAS-SYS or any of T1 to T4 monitors, and is relocatable, execute at
F00: