HMC7000 Series I/O Module Guide
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HMC7000 Series I/O Module Guide
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Common Terms for I/O Modules
This section defines some common terms used to describe various types of input and output modules.
The terms explained below are generic descriptions. Be sure to consult the datasheet for the specific
requirements when installing and wiring a module.
Digital Modules
Digital Modules provide physical connections and interpretations of input devices using discrete
signals. The input is represented in the PLC input registers as a 1 for the on state and 0 for the off
state. Each digital input terminal is associated with an internal Input Coil (X) in the tag database of the
HMC7000. Similarly, each digital output terminal is associated with an Output Coil (Y).
Analog Modules
Analog Modules provide physical connections and interpretations of input devices using analog signals.
The input range depends on the type of input device. Configure analog inputs to work with current or
voltage sources. Each analog input terminal is associated with an internal Input Register (XW) in the
tag database of the HMC7000. Similarly, each analog output terminal is associated with an Output
Register (YW).
Sinking versus Sourcing Inputs
These terms refer to the type of digital inputs or outputs used. A sourcing I/O provides a voltage
source, and a sinking I/O provides a ground. Any module that is not bidirectional (meaning current can
go in either direction) requires that the circuit conduct current in a specific direction.
For a sourcing module, the current flows out of the expansion module terminal and into the common
(signal ground) terminal. The term source indicates the terminal on the expansion module provides the
current to the switch contact or load.
For a sinking module, the current flows into the expansion module terminal and out of the common
terminal on the I/O module. The term sink indicates the terminal takes in the current from the switch
contact or load.
