1.308 Input

This page describes the device driver and the device window for the Input logical device. This device monitors one single input port of a PLC device and optionally associates a fault with this input port.

The Input logical device is part of the sat-nms framework for M&C of plain digital I/O functions. It does not interrogate a PLC device directly, but requires a low level device driver to do the physical communication. Examples for such drivers are the Fanuc-PLC9030 and the NAIS-FP0 PLC device drivers.

The Input device may be configured in various ways to match the requirements of almost all applications. Key features of the device are:

• The reported port states (default '0' / '1') may be translated to arbitrary strings (e.g. 'Door open' / 'Door closed').
• The device optionally may be configured to generate a fault if either the port is high or low.
• The description of the fault flag is customizable.

Device window pages

The following table shows which device window pages are available with this individual device type. Tool-bar functions not mentioned here are described at the general description of device windows .

• --- Shows / the (translated) PLC port state.
• --- The faults page.
• --- The device info page.
• --- The maintenance page. The configuration parameters described below are set at this page.

Configuration parameters

At the maintenance page of the device window there are a couple of configuration parameters which must be set to integrate the device into the VLC/M&C.

• parameter --- description

• inputPort --- The address of the PLC port to monitor. See the paragraph 'Port addressing' below for details.

• positions --- By default the device reports the state of the input as '0'/'1'. You may specify arbitrary texts for these states. 'positions' contains the two descriptions, separated by a comma. If you customize this setting, you should consider that other logical devices (e.g. a protection switch) may expect standard values like 0, 1, OFF or ON when reading this value.

• faultMonitoring --- Defines for which input states the device shall report a fault.

  • NONE --- Dont' report a fault
  • FAULTIF0 --- Report a fault if the input (physically) reads '0'.
  • FAULTIF1 --- Report a fault if the input (physically) reads '1'.

• faultText --- The text of the fault message. In the event log, changes of the fault state appear as ' ... text ... FAULT' or ' ... text ... OK'.

• commFaultId --- By default (commFaultId is empty) the device signals a communication fault if the summary fault of the PLC device get active. This may not be exactly what you want, because the PLC device may signal a fault which does not inhibit the switching or input sampling process. You may set commFaultId to the parameter ID of a fault flag which signals the desired condition. This makes the device ignore the PLC's summary fault and use the state of this fault flag as communication fault. The SatService IO-FEP driver for example offers such a fault flag which signals that actually no switching an no input interrogation is possible (faults.17 at the IO-FEP).

Fault flags

Port addressing

A device driver for a PLC gives access to it's I/O ports through a number of integer variables. Each variable stands for up to 64 input or output ports which are addressed by the bit position within the variable.

Port (bit-) addresses in the configuration of the logical I/O devices refer to such a variable which is provided by the PLC driver and also to the bit position within this variable. The syntax of a port address specification is:

<variable-identifier> + <bit-offset>

<bit-offset> is a decimal constant in the range 0 .. 63. You may replace the + character in the port address by a percent sign ( % ) and specify the bit offset in hexadecimal notation. This may be helpful for PLC types which use hexadecimal addresses.

Example: The port address ' FANUC.I00065+1 ' refers to the 2^1 bit in the variable ' I00065 ' provided by the ' FANUC ' device. In fact this addresses the input table register '%I00066' at the PLC. Other PLC drivers may use a different naming scheme for the variables, but the concept always is the same.

'initialized' condition

During the initialization phase of the M&C the state of physical inputs may be not yet known. To prevent the Input device from raising a fault during this phase, the Input device expects that the PLC driver provides an 'initialized' variable which is set true after the phsyical inputs have been read the first time after system start. The Input device will not raise a fault until it recognizes the PLC driver to be initialized.

The Input device derives the device name of the PLC from the configured input port address and reads the '.initialized' variable to get this state.

All PLC and IO-Controller drivers supplied by SatService GmbH provide this 'initialized' status variable. If you are using the Input device with other device types, be sure that the device provides this 'initialized' value or the Input device will not work as expected.

Remarks

• The Input device typically is used with PLC input ports. It however is not restricted to this. One application where the monitoring of output ports may make sense is the interrogation of ports which are controlled by program running in the PLC device itself.
• Using the 'positions' configuration setting you may reverse the polarity of the input. Set it to '1,0' and the device reports the state inverted. Please note, that the setting 'faultMonitoring' always refers to the physical state not to the translated one.
• The Input device works completely event driven, it introduces no noticeable delay between the change of the input and the state report. For a fast response you should tune the device thread IDLE time of the thread running the PLC driver to the lowest possible value which does not raise the overall CPU load above 20%. (recommended IDLE time for PLC drivers: 200ms)

Variables defined by this device driver