beautypg.com

Mstr block read operation, Mstr block read operation -197, 2 mstr block read operation – Delta RMC101 User Manual

Page 447

background image

Modbus Plus 5.3

Communications

5-197

Read Global Data:

Gets filled by the PLC with the number of

registers of global data available from the slave

Peer Cop Health:

Gives the number of registers to read from the

Peer Cop Health map.

5th-9th

Routing 1-5:

Read/Write Data:

The uses of these fields depend on whether

Modbus Plus or Modbus/TCP is being used.

Modbus Plus:

For local addresses, Routing 1 gives the node

address, and Routing 2 gives the data path (1-8) to use in
the node. Routing 3 through 5 are zeros. For more
complicated routing methods, refer to the section on routing
path structure in Modbus Plus Network Planning and
Installation Guide.

Modbus/TCP:

Routing 1 is broken into two bytes: the MSB

holds the Quantum backplane Slot ID of the NOE module,
and the LSB holds the Map Index, which should be zero for
the RMC. Routing 2 through 5 holds the four dot-separated
values of the RMC IP address (e.g. 192.168.0.5).

Global Data:

Routing 1 gives the address of the node to read

global data from. Routing 2 through 5 are zeros.

Peer Cop Health:

Unused.

Data area
A 4x (holding) register is given in this field (node). This register is the first of a block of data that
will either be written to the slave (in the case of a Write Data operation) or read into from the
slave (in the case of Read Data and Read Global Data operations).

Length
This integer gives the number of registers available for reading and writing in the data area.
Notice that this value serves as a maximum and does not indicate the actual number of registers
written or read, which is given in the 3rd register in the Control Block.

5.3.7.2 MSTR Block Read Operation

For general information on the MSTR Block, see Using the MSTR Modicon Ladder Logic Block.

Reading from Modbus Plus is described in Reading and Writing Modbus Plus Registers. Reading
from Modbus/TCP is described in Using the Modicon Quantum with the RMC Ethernet Module.

Control Block
In a Read operation, the nine control-block registers are assigned in as shown:

This manual is related to the following products: