Schneider Electric 890USE19600 Version 1.0 manual Data Exchange, Data and Status, Objects

Fieldbus Communications Support

Data Exchange

Introduction Process image data is exchanged between the STB NIB 1010 NIM and an INTERBUS fieldbus master in a bit-packed format.

Note: In this discussion, data and words described as input and output are defined relative to the master. For example, the master receives input data and transmits output data.

Data and Status		Data exchange between the island and the INTERBUS master involves three types
Objects		of objects:
			data objects—operating values the INTERBUS master either reads from the input
			modules or writes to the output modules
			status objects—module health records sent by I/O modules and read by the
		￿	INTERBUS master
			echo output data objects—sent by digital object modules to the INTERBUS
			master; these objects are usually a copy of the data objects, but they can contain
			useful information when a digital output point is configured to handle the result of
			a reflex action
		Standard Advantys STB I/O modules support all three of the above objects. Basic
		Advantys STB I/O modules support only data objects, not status or echo objects.
		The following table shows the relationship between different object types and
		different module types. It also shows the size of the different objects:
Module Type				Objects in the Input Data Image		Objects in the Output Data Image
				Objects	Size	Objects	Size
digital input				data	1 byte or less	does not apply
				status1	1 byte or less	does not apply
digital output				echo output data	1 byte or less	data	1 byte or less
				status1	1 byte or less	does not apply
analog input	channel 1			data	2 bytes	does not apply
				status2	1 byte	does not apply
	channel 2			data	2 bytes	does not apply
				status2	1 byte	does not apply
analog output	channel 1			status2	1 byte	data	2 bytes
	channel 2			status2	1 byte	data	2 bytes

1 Echo and status information is not available for every module. For example, basic I/O modules do not report this information. Refer to The Advantys STB Hardware Components Reference Guide (890 USE 172 00) for details.

2 Status information is not available for every analog module. For example, basic analog modules do not report status. Refer to The Advantys STB Hardware Components Reference Guide (890 USE 172 00) for details.

38 890USE19600 April 2004