Rockwell Automation 6008-SI IBM PC I/O SCNNR 6008-SI - Manual (Page 77)

Chapter 7
Scanner Management
7-10
The data returned by a successful autoconfigure can be divided into two
parts:
a fixed length part, 32 pairs of bytes. The first byte of each pair gives
information about the size and type of the adapter, and the second byte
gives fault information. For complete information, please see
”Autoconfigure and Link Status Information” in this chapter.
a variable length part, 0 to 16 bytes long, containing the new default
scan list. Each byte contains an adapter position in the form 4 x rack +
group / 2. The length of the scan list is packet.qmr_len – 2 x 32.
The time required to complete an autoconfigure request depends on the
baud rate and the number of adapters connected, as well as the size of each
adapter. For simplicity, we consider worst case, where each adapter
controls a full rack. In this case, the time to completion is 11 milliseconds
per connected adapter (7 ms at 115.2 Kbaud) plus 6 ms for each of the 32
possible adapter positions where no adapter is connected. Doing the
algebra, we have
T = 5 ms x adapters + 192 (57.6 Kbaud)
T = 1 ms x adapters + 192 (115.2 Kbaud)
Since no more than 16 adapters can be connected at once, worst-case time
for an autoconfigure is 272 ms at 57.6 Kbaud, 208 ms at 115.2 Kbaud. (If
16 adapters are connected, they can’t all be full racks, so this is actually a
longer time than true worst case.)
Link Status
A link status request returns the same information as an autoconfigure, but
link status differs from autoconfigure in three ways:
The scanner can execute a link status request while in any mode, not just
program mode.
The scanner doesn’t actually query possible adapters in doing a link
status. Rather, the scanner copies its internal status tables to the global
RAM.
Fault dependent groups and the current scan list are not changed by a
link status command.