The
BUTTON command (like some other commands only work on the designated
INPUT pins, which in the case of the 28X1 is port C. (Outputs are port d).
The command
Is trying to assign the tag “pushbutton” to port c pin 2 (physical pin 13)
Using port “a” as digital inputs is restricted to simple functions like:
IF porta 1 = 1 THEN GOTO xxxx
LET bit1 = porta 1