ABB Symphony Harmony Series Instruction page 52

Input Circuit Description
Input Circuit Connections
Control Logic
WBPEEUI240767B0
Input signal path and low isolation capacitance allow protec-
tion against fast transient-burst disturbance.
The threshold detection block circuits test the input voltage to
determine if it is at the proper voltage level to indicate an (on)
or (off) state. The output of this comparator is sent to a read
buffer in the control logic block. If an input is energized, it also
causes a corresponding input status LED on the front panel to
light.
The control logic block consists of buffers that hold the input
and status byte values. The I/O expander bus interface allows
the controller to read these bytes.
When an input signal is present at the proper voltage level, a
zener diode conducts (turns on) to cause current flow through
an optocoupler. Configurable jumpers (on IMDSI22) or fixed
resistors (on IMDSI13, IMDSI14 modules) select the turn-on
threshold and input voltage.
The optocoupler output causes a comparator output to go low.
This lights a corresponding status LED on the module front
panel to indicate an energized input. The I/O expander bus
interface transmits a logic one to the controller on the I/O
expander bus. When no input signal is present, no current
flows through the optocoupler. The front panel LED does not
light and the DSI module transmits a logic zero on the I/O
expander bus. Figure
NOTE: The components inside the dashed boxes in Figure
only on the module versions stated in the note.
The contact input signals connect to the 30-pin card edge con-
nector (P3), shown in Figure 2-1, using a termination cable
from a termination unit.
Function code 84 in the controller configuration accesses the
DSI module on the I/O expander bus. It also allows the control-
ler to automatically read point (input) data or status data from
2-2 shows the digital input circuit.
Control Logic
2-2 are mounted
2 - 3