PAK-I Datasheet, PDF (14/28 Pages) List of Unclassifed Manufacturers – 310 Ivy Glen Court

CHS
Negates the X register.
COMMCK
This command causes the Pak I to issue a
$22 response. You can use this to check
communications. The Pak I will always
respond with $20 plus the version number.
DIGIT
The DIGIT command accepts a single byte
as an argument and returns a single byte. If
the input byte is a zero, DIGIT returns an
ASCII +, and ASCII – or a blank character
depending on if the X register is positive,
negative, or zero. You can use this as a
SGN function, but it is mostly useful when
writing numbers in readable form.
If the input number is less than $7F, DIGIT
returns the ASCII digit from the X register
that you ask for. For example, if X contains
13.141 and you issue a DIGIT 1 command,
the return will be '3'. DIGIT 2 will return
'1'.
Numbers greater than $80 return ASCII
characters to the right of the decimal point.
So using the same example, if you issue a
DIGIT $81, the return will be '1'. DIGIT
$82 will return '4'.