I/O Devices Properties

Configuring an I/O Device involves specifying its properties using the Project Editor. The properties depend on both the protocol and I/O Device.

To configure an I/O Device:

1. In the Project Editor, select Communication | I/O Devices. The I/O Devices dialog displays.
2. In the Name field, type in a name for your I/O Device (PLC). The name needs to be unique in the CitectSCADA system, unless the I/O Device is defined in other I/O Servers (to provide redundancy). If redundancy is used, the I/O Device needs to then have the same I/O Device number and address for each I/O Server. use different I/O Device names for your primary and standby I/O Devices, otherwise I/O Device Cicode functions cannot differentiate between them. 31 characters maximum.
3. In the Number field, enter a unique number for the I/O Device (0-16383). 8 characters maximum. The number needs to be unique in the CitectSCADA system, unless the I/O Device is defined in other I/O Servers (to provide redundancy). If redundancy is used, the I/O Device needs to then have the same I/O Device number and address for each I/O Server. You may use the same device name, but if you want to use I/O Device Cicode functions, it is easier to have different I/O Device names.

4. Note: For Numbers, Protocol and Port Type - The same network number is used for redundancy (as stated above), however this implies that the Protocol is usually the same (though there maybe some special circumstances where devices support multiple protocols) and the Port modes are similar. i.e. a real world port reference, DISKDRV or MEMORY . If DISKDRV is being used, then redundant units (i.e. the same NUMBER) needs to be DISKDRV. This also applies for MEMORY mode.

4. In the Address field, enter the address of the I/O Device. 64 characters maximum. What you enter in this field is determined by the type of I/O Device (and protocol) used, as each has a different addressing strategy.
5. In the Protocol field, select the protocol you are using to communicate to the I/O Device. 16 characters maximum. Many I/O Devices support multiple protocols, dependent on the communication method chosen.
6. In the Port Name field, specify the port on the board to which the I/O Device is connected. 31 characters maximum. This is necessary to link the I/O Device to the port. For example Board1_Port1.

7. Note: There is a limit of 255 COMx ports on a server. To avoid this limitation restricting your number of remote I/O Devices, you can connect multiple remote I/O Devices to the same port as long as communication details (Telephone number, baud rateThe number of times per second a signal changes in a communication channel. While the baud rate directly affects the speed of data transmission, the term is often erroneously used to describe the data transfer rate. The correct measure for the data rate is bits per second (bps)., data bitsGroup of binary digits (bits) used to represent a single character of data in asynchronous transmission., stop bitsThe number of bits that signals the end of a character in asynchronous transmission. The number is usually 1 or 2. Stop bits are required in asynchronous transmissions because the irregular time gaps between transmitted characters makes it impossible for the server or I/O device to determine when the next character should arrive., and parityA communications error-checking procedure. The number of 1's must be the same (even or odd) for each group of bits transmitted without error.) are identical.

7. In the Startup mode field select the type of I/O Device redundancy:

   Primary	Enable immediate use of this communications channel. This is the default mode if no mode is specified.
   Standby	This channel will remain unused until the I/O Device configured with the primary channel becomes inoperative.
   StandbyWrite	This channel will remain unused until the I/O Device configured with the primary channel becomes inoperative. Write requests sent to the primary channel are also sent to this channel. Note: Do not use this mode for scheduled I/O devices because there is the possibility that the Standby I/O device write queue will never be cleaned up. When writing to a scheduled I/O device which it is not communicating, write requests are queued up until communication resumes. In case of using I/O device redundancy and StandbyWrite mode, Primary and Standby I/O devices have their own queues of pending write requests. If I/O device communication is controlled automatically by the communication schedule, then both queues are flushed when the schedule dial-time occurs. Where manual communication is controlled by the IODeviceControl Cicode function, only the Primary I/O device write queue is flushed and the Standby I/O device write queue will never be cleaned up.

   Note: To use Standby or StandbyWrite modes, you need to also configure a Primary I/O Device with the same I/O Device name, number and address.

8. In the Priority field type the order standby devices are promoted in if a primary I/O Device becomes inoperative during runtime. 8 characters maximum.

9. If there is more than one standby I/O Device configured for a cluster, you can use this field to give precedence to a particular standby device. If this field is left blank, priority will be automatically allocated to the device during project compilation, based on the priority settings of other standby devices and/or the order the devices were configured in.

   See I/O Device promotion.

9. In the Memory field, specify whether the I/O Device runs in Memory mode. 8 characters maximum. The default value is FALSE. If you select TRUE, the I/O Device will be created in memory and its values stored in memory at runtime. This may be useful if you are testing your system, before connecting physical I/O Devices, as memory mode stops CitectSCADA from communicating with physical I/O Devices. See Using Memory Mode.

10. Note: If a device is configured with Memory set to TRUE, the Port Name and Address fields can be left blank as they will not be used by the compiler or the I/O server at runtime.

10. In the Comment field, type in any useful comment. This field is optional and is not used at runtime.
11. Click Add to add a new record, or Replace to replace an existing one.

See Also

Fields implemented with extended forms (press F2).