Rockwell Automation 57C570 AutoMax PC3000 User Manual - Manual (Page 187)

18Ć5
See the following table for a description of the registers in the drop 0
area.
Table 18.6 ĆDescription of Registers in Drop 0 Area
Registers Description
Registers 4 Ć 7
(Drop Status Bits)
WARNING
THE DROP 0 STATUS BITS MUST BE USED IN AN
APPLICATION PROGRAM TO INDICATE NETWORK
COMMUNICATION FAILURE. FAILURE TO OBSERVE
THIS PRECAUTION MAY RESULT IN BODILY INJURY.
WARNING
THE USER MUST PROVIDE AN EXTERNAL,
HARDWIRED EMERGENCY STOP CIRCUIT OUTSIDE
OF THE CONTROLLER CIRCUITRY. THIS CIRCUIT
MUST DISABLE THE SYSTEM IN CASE OF IMPROPER
OPERATION. UNCONTROLLED MACHINE
OPERATION MAY RESULT IF THIS PROCEDURE IS
NOT FOLLOWED. FAILURE TO OBSERVE THIS
PRECAUTION COULD RESULT IN BODILY INJURY.
In the master, the drop status bits indicate which slave
drops are active on the network. The drop status bit will
be equal to 1 whenever the corresponding slave drop is
actively communicating with the master.
In the slave, the drop status bits indicate which drops
represented by that slave module are active on the
network. The drop status bits will be equal to 1 when the
corresponding drop is actively communicating with the
master. If any of these bits are equal to 0, it indicates that
the drop is either not represented by that slave module
or is not communicating with the master.
In a slave module, the drop 0 status bit (register 4, bit 0)
functions as the logical AND of the status bits of all the
drops that slave module represents. The drop 0 status
bit will be equal to 1 when ALL drops represented by
that slave module are actively communicating with the
master module. If any of the drops represented by the
slave are not communicating with the master, the drop 0
status bit will be equal to 0. Therefore, the drop 0 status
bit is used to indicate whether the slave module is
communicating properly. If a drop fails, the status bit will
be off a minimum of 120 milliseconds to allow detection
by an application task.
For example, in a slave module with a drop setting of 02
and a drop depth of 3, the drop 0 status bit will be equal
to 1 if the drop status bits for drops 2, 3, and 4 are also
equal to 1 (i.e., communicating with the master). Refer to
figure 18.2. If any or all of the three drops are not
communicating with the master, the drop 0 status bit will
be equal to 0.