[Coco] Detecting carts
robert.gault at att.net
Thu Jul 5 02:31:46 EDT 2012
Bill Pierce wrote:
> Hi guys,
> Anyone know of an easy way in "C" (or M/L sub) to detect the presence of certain catridges?
> RS Speech & Sound pak.
No idea about most of the paks but this should work with the Speech Sound pak as
long as no other pak does the same thing.
Two I/O bytes are used with this pak, $FF7D and $FF7E. The latter is used to
send data to the pak and when read shows the status of the pak. If $FF7E bit 7
(msb) is 0, the pak is busy processing a command.
With a Coco3 and MPI, $FF7E (for me) is 255 without a S&S pak and does not
change when POKEd. With a pak present, the following happens.
The manual says, "... you should first monitor the status byte to determine
whether or not the S/SC is ready to accept another character."
Likewise if the status bit is always high after sending a value to $FF7E, you
should not have an S/SC in the system. The converse result might be a false
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