Rockwell Automation 6008-SI IBM PC I/O SCNNR 6008-SI - Manual (Page 78)

Chapter 7
Scanner Management
7-11
To query the scanner about link status, simply issue an mr_wait function
call with C_LINKSTAT as its first argument.
Calling sequence:
status = mr_wait(C_LINKSTAT,
&packet
);
where:
packet is a QMR type packet. Note that the argument to mr_wait is a
pointer to the packet.
Returned values:
status and packet.qmr_stat as explained under General Form, above.
packet.qmr_data and packet.qmr_len contain exactly the same
information as is returned by an autoconfigure, except that the scan list
and fault dependent groups have not been disturbed. The scan list
length may also be up to 64 bytes long rather than just 16. For complete
information, please see ”Autoconfigure and Link Status Information”
later in this chapter.
Scan List
You can use a scan list request to tell the scanner to give a larger share of
its attention to some adapters at the expense of others. Though there are
only 32 possible adapter addresses, and only 16 of those can be occupied at
a time, the scan list can be up to 64 positions long.
The scan list and fault dependent group requests interact in one way:
Every adapter that is part of a fault dependent group must also be part of
the current scan list. If you try to violate this rule by specifying a new scan
list, one that omits some adapters that are still in fault groups, the scanner
returns an error code and leaves the old scan list in effect. To change the
scan list in that way you must first issue a fault dependent group command
that leaves the “orphan” adapters out of all fault groups.