PPoll() is similar to the 'traditional' API function
ibrpp().
It causes the interface board to perform a parallel poll, and stores
the parallel poll byte in the
location specified by result
. Bits 0 to 7
of the parallel poll byte correspond to the dio lines 1 to 8, with
a 1 indicating the corresponding dio line is asserted. The devices
on the bus you wish to poll should be configured beforehand with
PPollConfig().
The board must be controller-in-charge to perform a parallel poll.