PAK-I Datasheet, PDF (13/28 Pages) List of Unclassifed Manufacturers – 310 Ivy Glen Court

READX and RIO commands do not follow this
convention, but they take very little time to
execute anyway (less than 8uS).
To summarize, here are the ways you can
synchronize with the Pak I:
1. Delay long enough to insure the operation is
complete
2. Monitor the Enable/Busy line while Busy/Mode
is grounded. If you bring Enable/Busy low it
indicates that the Pak I is disabled. If the Pak I
brings the pin low, it means it is engaged in
operations.
3. Place a pull up resistor on the Busy/Mode pin.
This will cause the Busy/Mode pin to be high
when the Pak I is busy.
4. On commands that return status or ASCII digits,
you can wait until the data pin goes low.
Command Reference
ABS
Finds the absolute value of X. That is if X
is negative, negate it. If X is zero or
positive, leave it alone.
ADD
Adds X and Y leaving the result in X. Y is
unchanged. This command may take
approximately 110uS in the worst case.