TDE Instruments Digalox DPM72 User manual
Digalox® DPM72 RS485/Modbus interface
Instruction manual Rev-2022-07)
1. Description
The Digalox® DPM72 devices with Modbus interface can communicate as master or
slave with other DPM72 devices or devices from other manufacturers via the
Modbus RTU protocol Values from the device are available as display values,
values from other devices can be integrated into the display as remote values In
master mode, values can also be exchanged between two slaves with the help of a
buffer
2. Specification
•8 data bits, 1 stop bit
•Baud rate: adjustable up to 500,000 baud
•Parity: none, even, odd, space, mark
•¼ unit load, up to 128 participants
•External terminating resistor required
3. Electrical connections
DPM72
RS485
Rt = 120 - 270 Ω (external terminating resistor)
A
GND
A
B
620 Ω
Rt
4. Configuration – general
To configure a device, disconnect it from the Modbus network, short-circuit terminal
J8 and connect the device to a PC using an RS485 USB adapter "RS485 config"
appears on the display (if available), the device can now be configured using the
"Digalox® Manager" software After completing the configuration, open J8 again For
devices with a display, all values that are to be transferred must also be visible on
the display Devices without a display provide the first four configured display
values By setting jumpers J4-J6, different display values are provided accordingly
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5. Configuration – master
In master operating mode, up to 64 actions can be defined, which the master carries
out periodically They allow read or write access to the Modbus registers of the
slaves A delay between the messages can be set via the master delay parameter in
order to ensure compatibility with slower slaves
6. Byte order
By default, the devices transmit the values in the byte order 21436587 A different
byte order can be selected for the slave operating mode The master operating
mode allows the byte order to be set for each action
7. Modbus register
Read input registers – function code: 04
Address
hexadecimal)
Address
decimal)
Data type Description
0x00 0 Float32, IEEE-754 display value 1
0x02 2 Float32, IEEE-754 display value 2
0x04 4 Float32, IEEE-754 display value 3
0x06 6 Float32, IEEE-754 display value 4
0x08 8 Int64 display value 1
0x0C 12 Int64 display value 2
0x10 16 Int64 display value 3
0x14 20 Int64 display value 4
Read / write holding registers – function code: 03 / 16
Address
hexadecimal)
Address decimal) Data type Description
0x00 0 Float32, IEEE-754 remote value 1
0x02 2 Float32, IEEE-754 remote value 2
0x04 4 Float32, IEEE-754 remote value 3
0x06 6 Float32, IEEE-754 remote value 4
0x08 8 Int64 remote value 1
0x0C 12 Int64 remote value 2
0x10 16 Int64 remote value 3
0x14 20 Int64 remote value 4
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8. Status LEDs
There are three LEDs on the rear
of the device that indicate the
device and bus state:
•Power (green)
•Bus (orange)
•Act (red)
State Meaning
Power (green) shines Device on
Bus (orange) shines or flashes Bus active
Act (rot) flashes quickly or shines Device sends
Bus (orange) and Act (rot) flashes with a 2 second pause
[master only]
Slave does not
respond
9. Communication status display
The state of the Modbus communication is shown on the display
Display State Meaning
Symbol flashes Connection problems
M
M (Master) flashes Device communicates in master mode
S
S (Slave) flashes Device communicates in slave mode
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10. Messages on the display Master)
Display Meaning Solution
MB timeout Sx Slave x does not respond Check slave configuration,
increase master delay
MB Sx Wrong slave x responds Check slave configuration
MB exc Sx: y Slave x responds with Modbus
exception y
Read the error number in
the slave manual or the
Modbus standard
MB w/fc Sx Slave x responds with wrong function
code Check slave configuration
MB size Sx Response from slave x is wrong size Check slave configuration
MB res Sx
Confirmation from slave x for function
code 16 (write “Holding registers”) is
incorrect
Check slave configuration
MB func Sx Slave x responds with an
unsupported function code Check slave configuration
11. Messages on the display Slave) / Modbus exceptions:
Display Meaning Solution
MB illegal fc y
Unsupported function code y
received from the master; Modbus
exception 1 answered
Check master
configuration
MB illegal data
addr
Invalid register access requested by
master; Modbus exception 2
answered
Check master
configuration
12. Contact details
TDE Instruments GmbH, Gewerbestraße 8, D-71144 Steinenbronn
Phone: +49 7157 20801
E-mail: info@tde-instruments de
Internet: www tde-instruments de, www digalox com
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