Rockwell Automation 6008-SI IBM PC I/O SCNNR 6008-SI - Manual (Page 103)

Chapter 8
Block Transfer
8-13
The scanner places a module control byte (MCB) in the output image table
of the location of the BT modules discrete address when starting a read or
write BT.
Your program should never write to the output image bytes that correspond
to intelligent I/O modules; but if your program does, and happens to write
a valid MCB, the intelligent I/O module thinks the scanner is trying to do a
BT and responds accordingly. But the scanner doesn’t know anything
about a BT, so it tells the module “no thanks!” and sets the SO_OIT_ERR
bit in the operating status word. This indicates that a module tried to start
an unsolicited BT, one that the scanner itself knew nothing about.
This operating status bit stays set until your program resets it. Your
program should check once per program scan for this operating bit and
then should reset it:
if ( g_op_stat & SO_OIT_ERR ) {
/* take appropriate action for your application, and
... */
g_op_stat &= ~SO_OIT_ERR; /* clear the bit */
}
In addition, the library routines keep a count in global variable g_oit_err
of notices received from the scanner about unsolicited BTs.
A common configuration of PC based control systems using a scanner, is
for the scanner to communicate with PLC5 family processors set up for
adapter mode operation. In this configuration, the scanner is
communicating with the PLC5 over the remote I/O link and the PLC5
emulates a 1771–ASB adapter module. The scanner has no way of
knowing it’s transferring data directly with a PLC, it thinks it is
communicating with an adapter module.
The PLC5, while in adapter mode, has only local I/O. The PLC5’s remote
I/O network is dedicated to the scanner. Likewise, the physical port of the
PLC5 used for the remote I/O link, is dedicated to the scanner, because this
is where the scanner’s I/O link is physically connected. The baud rate of
the I/O link must be 57.6 KBaud, because the PLC5 communicates only at
57.6 KBaud.
Because the PLC5 does not have remote I/O of its own, rack 3 of the
PLC5’s I/O image table is reserved for communications with the scanner.
Rack 3 normally would have been used by the PLC5 as a remote rack on
its remote I/O network. But rack 3 now becomes the bridge between the
PCbus I/O scanner and the PLC5.
Unsolicited
Block Transfer
Block Transfer to PLC5's in
Adapter Mode