Modbus Data Formats - Ametek AN-3100D Installation And Configuration Manual

APPENDIX B
M D
ODBUS ATA
The AN3100D Modbus operates as a Master or Slave in both Modbus RTU and
Modbus TCP/IP modes. The AN3100D Modbus port will transmit the ON/OFF
Status (called 'Alarms') and when equipped with the SER option, the timestamp
recorded for every alarm and return to normal occurrence (called 'Events').
Alarm ON/OFF Status is provided by reading 16-bit holding registers (Modbus
Function 03) with a single bit designated per input. A 48 input system would
indicate the status of all alarms using three 16-bit holding registers.
Event Data is provided by reading six 16-bit holding registers (Modbus Function
03) that contain the time, date, input number and alarm status for each event.
An event could be an input going into alarm or returning to normal. Event data
is provided in blocks of ten events for a total of sixty 16-bit holding registers. If
there are no new events since the last Modbus poll, it will return all FF's. If there
are more than 10 events in the buffer, then it will continue to submit 10 events
every poll until there are no new events.
The system has the capability of operating with three distinct data formats: point
mode, alarm state mode and AN3135 mode. The latter is designed to be
compatible with existing AN-3100C Modbus installations. All these formats are
embedded within Modbus data registers for transmission and reception.
A selection of Modbus function may be used and these vary depending on the
whether the AN-3100D is operating as Modbus master or slave.
Function Description
3 Read Holding Registers Words
6 Preset Single Register
7 Read Exception Status
Preset Multiple
16 Registers
17 Report Slave ID
A function value of 03 (Read Holding Registers) is set to read alarm data from
the system (in slave configuration). Function values 06 (Preset Single Register)
and 16 (Preset Multiple Registers) are used to write fault and control data.
Single and multiple register writes are supported. Exception status responses
(function 07) and Slave ID (function 17) are also supported. Exception codes for
unrecognized received messages are also included.
The Modbus functions are enabled by a software switch and require a key to
enable them, which is supplied by AMETEK. This may be done prior to delivery
or retrofitted to installed systems.
AN-3100D ANNUNCIATOR INSTALLATION AND CONFIGURATION MANUAL
F
ORMATS
Data Units
Words
Bytes
Words
Bytes
Data Direction
Master Slave
Input Output
Output Input
Input
Output
Output
Input
Input Output
i.
AN-3100D
Supported Mode
Master or slave
Slave only
Slave only
Master or slave
Slave only
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