Schneider Electric 890USE17700 manual Island’s Process Image Blocks, Output Data

Advanced Configuration Features

The Island’s Process Image Blocks

Summary	Two blocks of registers in the island’s data image (See The Data Image, p. 166) are
	the focus for this discussion. The first block is the output data process image, which
	starts at register 40001 and goes to register 44096. The other block is the input data
	and I/O status process image, which also consumes 4096 registers
	(45392 through 49487). The registers in each block are used to report island bus
	device status and to dynamically exchange input or output data between the fieldbus
	master and the island’s I/O modules.
Output Data	The output data block (registers 40001 through 44096) handles the output data
Process Image	process image. This process image is a Modbus representation of the control data
	that has just been written from the fieldbus master to the NIM. Only data for the
	island’s output modules is written to this block.
	Output data is organized in 16-bit register format. One or more registers are
	dedicated to the data for each output module on the island bus.
	For example, say you are using a two-channel digital output module as the first
	output module on your island bus. Output 1 is on and output 2 is off. This information
	would be reported in the first register in the output data process image, and it would
	look like this:
	register 40001																output data
		15		14	13	12	11	10	9	8	7	6	5	4	3	2	1		0
																					1
																				0
																		always 0
	where:
			Normally, a value of 1 in bit 0 indicates that output 1 is on.

￿Normally, a value of 0 in bit 1 indicates that output 2 is off. The remaining bits in the register are not used.

Some output modules, such as the one in the example above, utilize a single data register. Others may require multiple registers. An analog output module, for example, would use separate registers to represent the values for each channel, and might use the 11 or 12 most significant bits to display analog values in

IEC format.

Registers are allocated to output modules in the output data block according to their addresses on the island bus. Register 40001 always contains the data for the first output module on the island—the output module closest to the NIM.

Note: The requirements of each output module in the Advantys STB family are described in the Advantys STB Hardware Components Reference Guide (890 USE 172).

A detailed view of how the registers are implemented in the output data block is shown in the process image example.

168 890USE17700 April 2004