Moore Industries NET Concentrator System AOM, Руководство пользователя

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NET Concentrator System
®
NCS
- 34 -
Moore Industries-International, Inc.
www.miinet.com
NCS as MODBUS Slave
Each Interface Module is designed to be accessed
using MODBUS RTU and/or MODBUS/TCP
communication. The section below supplies all of
the information necessary to reference the MODBUS
register map and program a generic (third party)
MODBUS RTU master.
MODBUS RTU Support
The two RS-485 ports on the Interface Module act
as independent MODBUS RTU slaves, masters,
or in Peer to Peer mode. The MODBUS registers
allow access to process variable data and status
information. See Appendix B for a complete list of
available MODBUS registers.
In order to access the Interface Module MODBUS
registers via MODBUS RTU, you must ensure proper
configuration of the MODBUS RTU port and the
MODBUS master.
To use the Interface Module as a MODBUS slave,
the MODBUS RTU port(s) must first be configured
with the MODBUS slave address, baud rate, parity,
character timeout and response delay.
Next, you will need to configure the master which
will query the NCS to use the same baud rate and
character format as the Interface Module. Finally, the
Master will need to be programmed with MODBUS
register addresses to be polled and poll scheduling
information. Refer to the MODBUS Configuration
portion of this manual for information on configuring
the NCS.
To use the Interface Module as a MODBUS master,
refer to the
Configuring the Interface Module as a
MODBUS Master
section of the user’s manual.
MODBUS TCP Support
MODBUS/TCP is supported according to the
document, “
Open MODBUS/TCP Specification”
,
release 1.0, 29th, March1999, by Schneider Electric.
The MODBUS registers allow access to process
variable data and status information. See Appendix B
for a complete list of available MODBUS registers.
In order to access the Interface Module MODBUS
registers via MODBUS/TCP, the MODBUS/TCP
master must be configured to poll the NCS’ IP
address. Ensure that the IP addresses of the
MODBUS/TCP master and MODBUS/TCP slave are
valid IP addresses for the respective network. In
some instances it may be necessary to consult with on
site IT personnel to prevent Ethernet communication
errors.
Accessing Real-Time Data
At startup, the Interface Module will perform an
initialization sequence to detect all connected I/O
modules. If it recognizes the connected device, it
will mark the module as active in preparation for data
scanning. After detecting connected modules, the
Interface Module will begin continuous polling for the
process variable and status of each module. In the
case of Input Modules, the returned data is stored
locally in the Interface Module’s MODBUS
registers/coils. For Output Modules, the data in the
MODBUS registers is written to each output channel.
The data can be accessed by the configuration
software, MODBUS RTU master,
MODBUS/TCP server or web server. The Interface
Module continuously polls all connected I/O modules.
Reading and Writing Primary Variables
Process variables are read using MODBUS function
code 3 or 4. Process variables are written using
MODBUS function code 16. When using MODBUS
RTU (RS-485), write commands from MODBUS hosts
are limited to 60 registers. Each process variable or
channel in each of the TIM, AIM and AOM modules
(four channels each) can be configured as an integer
or 32-bit floating point. If configured as an integer one
MODBUS register is used per channel. Each 32-bit
floating-point process variable will be mapped to two
MODBUS registers; by default, the lower numbered
MODBUS register will hold the least-significant-word
(LSW), and the higher numbered MODBUS register
will hold the most-significant-word (MSW) of the 32-
bit value. The ROM and DIM modules use eight
MODBUS registers; one for each of the eight I/O
channels.
For MODBUS Masters or clients that support swapped
floating point, the Interface Module provides a setting
to change the default word order using the
MODBUS
properties
page of the web server. Each floating point
variable is also mapped to a single 16 bit register as
a scaled integer. Refer to the Scaled Integers section
for more information.