MDO16GNS October 2005 – Issue 2
11
Triguard
SC300E MDO16GNS 16-Channel D/O Module 48Vdc
Common Interface
The three discrete control circuits in the common interface (A, B, and C) 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 diagnostics, on-line/off-line status and
signal status read/write cycles to and from the SC300E 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 main processors for verification. The on-line/off-line status is determined by the
main processors. 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 main processors 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 or a voting discrepancy.
