Rockwell Automation 198 Series C Modular DeviceNet Starter Auxiliary User Manual - Manual (Page 133)

Troubleshooting 6-3
Publication 198-UM002A-EN-P December 2001
many products fail to function properly, and can begin to corrupt other messages on the
network. This product contains a bus voltage monitor at Attribute 30 of the DeviceNet
interface object (class 180) in the DeviceNet Interface Object. This value can be read and
used to reposition or add power supplies so that low voltage conditions do not occur on the
bus. If they do occur, the MDSA product will stop transmitting at approximately 10V, and will
execute a reset sequence when the voltage returns to approximately 11V.
Excessive Number of Modules
The MDSA has a built-in auto-configuration identification system that allows the customer to
order the modules in virtually any way. However, there are a few limitations to this system.
The first is that the MDSA system only supports 16 I/O modules in addition to DeviceNet
module. If this number is exceeded, Attribute 25, I/O error code, of the DeviceNet interface
object will return a 6, Too Many Modules. The present module offerings can be mixed in
any quantity up to 16.
Invalid ID
From time to time, Rockwell Automation will be introducing new modules. As a
consequence, if a new module type is added to an existing system, it might not be supported.
The I/O error code is 4, Invalid ID. This means that the MDSA module recognizes the
presence of a module, but does not have the necessary software to properly operate the
module. Contact your local Allen-Bradley Sales Office for DeviceNet module upgrade
information.
Checksum Error
The MDSA system constantly monitors the signals going to and from the various modules.
Whenever possible, the source and most likely cause is identified. I/O error code 7, CSUM
error, is produced whenever highly transient interruption of the signal occurs. Environments
that have excessive vibration or shock, or where continuous voltage transients occur would
most likely cause this error to occur. Attribute 26, error location, of the DeviceNet interface
object (class 180) points to the most likely source of the problem. When investigating an I/O
error code 7, begin by inspecting the module immediately preceding it for physical damage or
discontinuity. Then begin to check the environment for vibration and electrical transients.
Discontinuity Error
I/O error code 8, Discontinuity, is generated whenever one or more of the signal paths in
the system appears to be open. This could occur from improper module installation, or
connector damage.