ibln() checks for the presence of a device, by attempting to address
it as a listener. ud
specifies the GPIB
interface board which should check for listeners. If ud
is a device descriptor, then the device's access board is used.
The GPIB address to check is specified by the
pad
and sad
arguments.
pad
specifies the primary address, 0 through 30
are valid values. sad
gives the secondary
address, and may be a value from 0x60 through 0x7e (96 through 126), or
one of the constants NO_SAD or ALL_SAD. NO_SAD indicates that no
secondary addressing is to be used, and ALL_SAD indicates that
all secondary addresses should be checked.
If the board finds a listener at the specified GPIB address(es), then the
variable specified by the pointer found_listener
is set to a nonzero value. If no listener is found, the variable is set
to zero.
The board must be controller-in-charge to perform this function. Also, it must have the capability to monitor the NDAC bus line (see iblines()).