Rockwell Automation 1790D-XXXX DeviceNet Digital Base D-Shell Module CompactBlock LDX I/O - Manual (Page 18)

18 DeviceNet Digital Base D-Shell Block CompactBlock LDX I/O
Publication 1790-IN007C-EN-P - May 2006
Cable Break Procedure
A cable break in any location between either of the following
produces data of 1 in the data table for all inputs down stream of the
cable break.
• Base and digital input expansion module
• Digital input expansion module and another digital input
expansion module
All digital-expansion inputs turn on if the expansion cable is
removed. No status is in the produced assembly. Attribute 101 in the
identity object reports module faults. If no faults are present, an
explicit message GET command returns 0. If the ribbon cable is
disconnected, it returns 0x04, which is for module location change.
The module LED also flashes indicating a fault if an expansion is
disconnected. To determine if the data is valid, continuously send an
explicit message to the module to check the status of the input
conditions since no status word is in the I/O mapping data table.
• Class = 1
• Instance = 1
• Attribute = 101 (0x65)
To detect the loss of communication to the expansion module, use
one of these methods.
• If an unused input is available, tie the unused input on the last
expansion low. If that input goes high with a value of 1, a loss
of communication to the expansion or expansions occurred.
• If no unused input is available, check expansion inputs for the
condition of all on. To check validity in this case, send an
explicit message to the identity object class 1, instance 1,
attribute 101 (0x65). A returned value of 0 indicates the input
data is good.