PAK-IV Datasheet, PDF (8/14 Pages) List of Unclassifed Manufacturers – Using the PAK-IV I/O Coprocessor

Command Reference
BANKSEL
Selects BANK A or BANK B I/O. All operations that require a pin number (from
0 to 7) will use the currently selected bank.
BITREAD
Reads the logical state of the specified pin (1 or 0). This command does not
automatically force the pin into the input state. Returns a 0 or 1 byte.
CHECK
Communications check and version identify. Always returns $41 ($4 for this
PAK, 1 for version number).
COUNT
Count returns the number of transitions on the specified pin during the interval
you ask for. Send the period (16-bits) in 4uS units. The PAK-IV will return a zero
and the 16-bit count.
FREQOUT
This command emits a tone for a specified period on a particular pin. You'll want
to filter the output with an RC network to filter the high-frequency noise
generated. Send the frequency in hertz (two bytes) and the duration in
milliseconds (also two bytes). The PAK-IV returns 0.
FREQOUT2
This command emits two tones for a specified period on a particular pin. You'll
want to filter the output with an RC network to filter the high-frequency noise
generated. Send the first frequency in Hertz (two bytes), the second frequency in
Hertz (two bytes) and the duration in milliseconds (also two bytes). The PAK-IV
returns 0.
GETRAND
You can use this command to read a number that is suitable for seeding a random
number generator. This number is actually a free-running clock inside the PAK-
IV. The PAK-IV will return a zero and the quasi-random byte.
HIGH
Forces the specified pin to be an output and outputs a 1 on that pin. Always
returns 0.
INPUT
Converts the pin number to an input. Always returns zero.