Rockwell Automation MDO32BNS 32-Channel Digital Output Module - Manual (Page 13)

MDO32BNS October 2005 – Issue 7 13
Triguard SC300E MDO32BNS 32-Channel Digital Output Module
COMMON INTERFACE
The three discrete control circuits in the Common Interface (A, B, and C) (Figure 2-6) are each
responsible for the control of the corresponding one third of the I/O module circuits. Each
control circuit comprises a microcontroller with a dedicated watchdog, data buffers and shared
RAM. The circuit is powered via the module and permits live insertion of replacement modules.
The microcontrollers co-ordinate I/O signal processing, signal path diagnostics, on-line/off-line
status and signal status read/write cycles to and from the system processors via an I/O
communications bus. All I/O modules have an identification code which is read by the
Common Interface and passed to the MPPs for verification. The on-line/off-line status is
determined by the MPPs. If, for maintenance purposes, the On/Off Line Request switch on the
front of the module is operated, the action is read by all three microcontrollers and the request
passed to the MPPs which may then grant the request. The watchdog on each microcontroller
extinguishes the Health LED on the I/O module front panel in the event of a microcontroller
failure, LFD failure, a voting discrepancy, loss of field supply or open circuit conditions.
SYSTEM CONFIGURATION
The Digital Output module requires a ‘dual-slot hot repair’ configuration in order to maintain any
normally energised field loops during repair. We recommend that the ‘dual-slot hot repair’
configuration is used for all output modules. The ‘dual-slot’ configuration does not require the
hot repair slot to be populated. If the hot repair partner module is fitted during normal operation,
the output module pair should be de-rated by 50%; unless forced air-cooling is used.
NOTE
Fitted Hot Repair partner modules should be bought on-line as part of a regular maintenance
cycle to allow full diagnostic reporting for both modules.
The Digital Output module has a relatively high power dissipation which places some
constraints on its use in convection cooled systems. As each Digital output module will
dissipate 59W when run at full capacity we recommend that these modules are configured in
the lowest chassis within each cabinet bay. If Digital Output modules are configured in slots
located above a fully loaded Digital Output module we recommend that the module is de-
rated by 50%. When forced air-cooling is applied to a system to aid heat dissipation then
these limitations are removed. When configuring a system care should be taken to ensure that
the maximum working temperature of 60 C is not exceeded in the applications maximum
ambient conditions.