Allen-Bradley micrologix 1500, Руководство пользователя

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Publication 1764-UM001A-US-P
Understanding Communication Protocols E-17
Modbus RTU Slave
Communication Protocol
(MicroLogix 1764-LSP
and 1764-LRP Series B
processors only)
Modbus RTU Slave is a Half-Duplex, master-slave communications protocol. The
Modbus network master initiates and controls all communications on the network.
Modbus protocol allows a single master to communicate with a maximum of 255
slave devices.
When a MicroLogix 1200 or 1500 Communications port is configured for
Modbus RTU Slave operation, the user must define where Modbus data (coils,
contacts, and registers) is mapped into the MicroLogix data space.
The Modbus address space is comprised of seven distinct memory ranges. Four of
these ranges can be mapped into MicroLogix data files. Three Modbus ranges are
fixed to MicroLogix file 2, the Status file. The table below illustrates Modbus to
MicroLogix mappings.
For more information on the MicroLogix 1500 configuration parameters for
Modbus Slave RTU (Remote Terminal Unit transmission mode) protocol, refer to
the MicroLogix 1200 and 1500 Programmable Controllers Instruction Set
Reference Manual, publication 1762-RM001A-US-P. For more information about
the Modbus Slave protocol, see the Modbus Protocol Specifications (available from
http://www.modicon.com/techpubs/).
Table E.5 Modbus to MicroLogix Memory Map
Modbus Addressing Description Valid MicroLogix Addressing
File Type Data File Number Address
0001 to 4096 Read/Write Modbus Coil Data space Bit (B) or Integer (N) 3 to 255 bits 0 to 4095
10001 to 14096 Read-Only Modbus Contact Data space Bit (B) or Integer (N) 3 to 255 bits 0 to 4095
30001 to 30256 Read-Only Modbus Input Register space Bit (B) or Integer (N) 3 to 255 words 0 to 255
30501 to 30532 Modbus Communication Parameters Communication Status
Files
2 words 0 to 31
31501 to 31566 Read-Only System Status File space Status (S) 2 words 32 to 65
40001 to 40256 Read/Write Modbus Holding Register
space Bit (B) or Integer (N) 3 to 255 words 0 to 255
41501 to 41566 Read/Write System Status File space Status (S) 2 words 0 to 65
AB Spares