Modbus Interface Reference

The EM-482 operates as a Modbus gateway, listening for Modbus TCP connections on port 502 (configurable). It supports connections from standard Modbus TCP client applications. Windows client software for basic testing is available for download here.

Upon receiving a connection request, the EM-482 checks its list of active clients. If the maximum list size (as per technical specifications) has not been reached, the new client is accepted.

Once connected, the EM-482 processes Modbus requests from the client. In RS-485 Slave Mode, it also accepts requests from a Modbus Master on the RS-485 bus.

Request Processing

The device analyzes each request based on the requested function and the client’s access rights (determined by passwords entered).

• Blocked Requests: If a request is blocked due to insufficient rights, the EM-482 sends back a Modbus exception (default code 1).
• Internal Requests: If the request addresses the EM-482 itself, it is processed internally, and a reply is sent back.
• Redirection:
  • RS-485 Master Mode: Requests for other devices are converted (Modbus TCP/RTU/ASCII) and redirected to the RS-485 bus. The RS-485 indicator lights up while waiting for a response.
  • Remote Server: If configured, requests can be redirected to a remote Modbus TCP server via Ethernet or GSM/LTE.

Caution

Ensure there are no duplicate Modbus addresses (identifiers) across the RS-485 bus and the remote Modbus TCP server network. The response is accepted from the first responding device.

Caution

Ensure there are no redirection loops. E.g. the remote server address is not the EM-482 own address, etc. Redirection loops cause the responses to take longer, tend to cause exceptions or connection losses.

If a valid response is received, the EM-482 forwards it back to the client.

Troubleshooting

• Exception Illegal Function (Code 1) is returned for a request: Sent either by EM-482 (if insufficient rights for the request) or by the target device (if the request unsupported). Check the EM-482 settings (Protection group) for protection settings. Send the correct password to the EM-482 before using this request. Try allowing these requests, or try some other request.
• Exception Gateway Path Unavailable (Code 10 or 0x0A) is returned for a request: Sent if the request cannot be redirected. Check the connection to the remote is configured and established (if the target should be requested using Modbus TCP). Check the Modbus Master mode is configured (if the target should be requested using Modbus RTU/ASCII). Check the Modbus address ranges in EM-482 settings for the redirection destinations.
• Exception Target Device Failed to Respond (Code 11 or 0x0B) is returned: Sent if no response is received from the target device. Check the device settings match the EM-482 configuration for RS-485 (baudrate and parity in particular). Check the target device is powered on.
• Some exception (not 1, 10 or 11) is returned: Sent by the target device if it could not perform the request or produce the response data. Check the device manual. Try some other request.
• The data has been acquired, but the values seem wrong: Check the device manual. Ensure the Modbus device address and Modbus register address in the request are correct. Check the data formatting in the Modbus client software (which is sending this request). Try dividing the acquired value by 10, 100 or 1000.

Table 1 - Standard Modbus Exception Codes

Code	Exception	Description
1	ILLEGAL FUNCTION	The received function code cannot be processed
2	ILLEGAL DATA ADDRESS	The data address specified in the request is not available
3	ILLEGAL DATA VALUE	The value contained in the request data field is invalid value
4	DEVICE FAILURE	Unrecoverable error has occurred when the addressee has tried to perform the requested action
5	ACKNOWLEDGE	The addressee accepted the request and processed it, but it takes a long time
6	DEVICE BUSY	The addressee is busy processing the command. The client can retry the request later
8	MEMORY PARITY ERROR	The parity error was detected when the addressee has tried to read the extended memory
10	GATEWAY PATHS NOT AVAILABLE	The gateway cannot redirect the request, since there is no path (connection) to the addressee
11	TARGET DEVICE FAILED TO RESPOND TO GATEWAY	The gateway did not receive a response to the forwarded request, because the addressee did not respond in time

Configuration via Modbus

The EM-482 can be configured using any Modbus TCP client.

1. Connect: Use the EM-482’s IP address (configured manually or provided by the Wi-Fi access point, see its corresponding manual on how to check the address) and Modbus ID (default 111).
2. Enter Password: Write the password (default setup access password is in the parameter list, Protection group ) into the password registers (see Current Mode Parameters).
3. Verify Mode: If the password is correct, the Mode register will read 1 (Setup Mode).

Managing Settings

In Setup Mode, you can modify the Changeable Settings registers.

• Save Changes: Write 2 to the Command Register. Verify by comparing changeable parameters with saved parameters.
• Save & Apply: Write 4 to the Command Register. Applies Modbus parameters immediately without restart.
• Cancel Changes: Write 9 to the Command Register. Reverts changeable parameters to saved values.
• Factory Reset: Write 444 to the Command Register. Resets all settings to defaults.
• Restart Device: Write 1 to the Command Register. Required for some settings to take effect.
• Exit Setup Mode: Write 0 to the first password register (100). This clears the password and command registers.

EM-482 Parameters

Table 2 - Parameter Data Formats

Parameter	Range of values	Description	Number of occupied registers
Number	0 – 65535	Integer number (16 bit) in standard range of Modbus register values	1
Number	0 – 4294967295 in two registers, MSB part – first	Integer number, which value can exceed the limit for Modbus register (65535)	2
Character string	In every register – number of 0 to 255 - ASCII character code or 0 (the end of string)	A set of values, each of which is equal to the code of one character in the ASCII encoding. If the string is shorter than the maximum length, the code 0 is placed after the last character.	Max. length of string for this parameter
IP-address (IP-mask)	In every register – one byte (0 – 255)	Set of four byte of address IPv4, from left to right	4
MAC-address	In every register – one byte (0 – 255)	Set of six byte of address MAC-48, from left to right	6

Table 3 - Parameter Groups

Group	Description	Access	Address
Device description	Device and firmware identification	Any mode, read only	0 – 3
Current mode	Access and general commands controls	Password entry is available in any mode, command entry - only in setup mode (after password entry)	100 – 120
Current status	Interfaces and software modules operation, current time and statistics	Any mode, read only	121 – 177, 2000–2005
Changeable settings	Interfaces and features selection and configuration	Only in setup mode, reading or writing	300 – 899, 5250 – 5499
Active settings	The configuration being used by the device at the moment	In any mode, read only	2300 – 2899, 5500 – 5749
Saved settings	This set is saved regardless the power of the device and is used at restart	Only in mode of setting, read only	3300 – 3899, 5750 – 5999

Device Description Parameters

Table 4 - Device Description Parameters

Parameter	Description	Address
Device type	The code that defines the Modbus device for the manufacturer (31 – EM-482)	0
Firmware version	Firmware version of embedded software	1
Check code	CRC32 of firmware of embedded software	2 – 3

Current Mode Parameters

Table 5 - Current Mode Parameters

Parameter	Range of values	Initial value	Description	Address
Entered password	String of characters	0	When entering a valid password, the client is given the appropriate permission (see registers 510 - 569)	100 – 119
			When you enter an empty string, the client rights are reset to the rights level at the time of connection
Control command	0 – 65407, writing in the configuration mode	0	See Table 5.1 for the list of commands.	120

Table 5.1 - Control Commands (Register 120)

Value	Command	Description
0	No activity	No action performed
1	Restart	Restart the EM-482 device
2	Save	Save settings changes via Modbus
3	Apply	Apply settings without restarting (Modbus and user’s parameters only)
4	Save and apply	Execute “Save” then “Apply” commands
9	Cancel	Revert to saved settings
51	Apply for Modbus	Apply settings for Modbus and RS-485 only
59	Apply for User’s	Apply settings for user’s custom registers only
444	Factory Reset	Reset settings to factory defaults
35381	Start clock setting	Allow access to clock setting registers
35431	Cancel clock setting	Close access to clock setting registers without changes
40959	Update task memory	Erase the logic program (re-read if memory card is inserted)
64893	Download Updates	Download latest firmware from cloud to the loaded file
65397	Update Firmware	Program firmware from the loaded file
65407	Revert Firmware	Return to the factory firmware file

Current Status Parameters

Table 6 - Current Status Parameters

Parameter	Description	Address
Mode (for details see reg. 122)	0: User’s mode;	121
	1: Setting mode
Tabs of access	See Table 6.1 for the list of access bits.	122
Time, min	Number of minutes since the moment of start-up	123 – 124
Number of TCP clients	Number of occupied connections of TCP	125
Limit of TCP clients	Number of prospective clients of TCP	126
Load of RS-485, query/s	Total number of query/s via RS-485	127
Effective load of RS-485, query/s	Number of responds without errors via RS-485 per second	128
Load of RS-485 per second, %	Load of RS-485 for the last second considering the set rate of RS-485 and time of inactivity	129
Load of RS-485 per minute, %	Load of RS-485 for the last minute	130
Load of RS-485 for 5 minutes, %	Load of RS-485 for the last 5 minutes	131
Load of Modbus TCP, query/s	The number of queries received from clients via Modbus TCP per second	132
Effective load of Modbus TCP, query/s	Number of responds without errors being sent to the client via Modbus TCP per second	133
Load of Wi-Fi, kB/s	Load of Wi-Fi channel	134
Unused parameter	The parameter is reserved for compatibility	135
Max. number of clients of TCP	Maximal number of simultaneously connected clients via TCP – from the moment of start up	136
Max. load of Modbus TCP, query/s	Maximal number of queries received per second from the clients via Modbus TCP – from the moment of start up	137
Max. load of RS-485, %	Maximal load of RS-485 for 5 minutes – from the moment of start up	138
Max. load of Wi-Fi, kB/s	Maximal load of Wi-Fi – from the moment of start up	139
Current IP-address of Wi-Fi	IP-address, by which EM-482 device is accessible in the network	140 – 143
Current MAC-address of Wi-Fi	MAC-address, by which EM-482 is detected in the network	144 – 149
Unused parameter	The parameter is reserved for compatibility	150 – 164
Time to connect to the data collection server	0 – connection to the data collection server is set;	165
	1 – connection to the data collection server is performed;
	2 – 65534: the number of seconds before reconnecting;
	65535: connection to the server is not used
Number of programmed restarts	Number of restarts in accordance to the user setting – for total operational time	166
Number of critical errors	Number of noted errors (failures) causing the restart of the device – for total operational time	167
Total operation time, min	The number of minutes of operating time - for the total operational time	168 – 169
Unused parameter	The parameter is reserved for compatibility	170 – 174
Power supply voltage, mV	Voltage at the product power supply terminals	175
Time to connect to a remote TCP server, s	0 – connection to the remote server is set;	176
	1 – connecting to the remote server;
	2 – 65534: the number of seconds before reconnecting;
	65535: connection to a remote TCP server is not used
Status of a connection to a remote TCP server	0 – the connection is not set;	177
	1 – connection is set;
Firmware Download Status Bits	See Table 6.2 for the list of status bits.	2004
Firmware file download progress (х 0.01%)	Proportion of downloaded data size to total file size.	2005
	10000 – File fully downloaded
Firmware File Header	The string identifier of the version, e.g., “EM-482, ver.10”.	2030 – 2061
	A blank string indicates the file is either unverified yet or invalid

Table 6.1 - Tabs of Access Bits (Register 122)

Bit	Description	Value 0	Value 1
0	Permission to obtain RS-485 reading rights (via password)	Cannot be obtained	Can be obtained
1	Current RS-485 reading permission	No permission	Permission granted
2	Permission to obtain RS-485 write/control rights (via password)	Cannot be obtained	Can be obtained
3	Current RS-485 write/control permission	No permission	Permission granted
4	Permission to obtain EM-482 register access (via password)	Cannot be obtained	Can be obtained
5	Current EM-482 register access permission	No permission	Permission granted
6	Reserved	-	Always 1
7	Permission to configure EM-482	No permission	Permission granted
8	Reserved	Always 0	-
9	Connection right	-	Client has right (Always 1)

Table 6.2 - Firmware Download Status Bits (Register 2004)

Bit	Status	Value 0	Value 1
1	Busy Status	Waiting for command	File download in progress
2	Update Download Error	No error	Download error occurred
3	Server Connection	No connection	Connected to server
4	File Data Reception	No data received	Some file data received
6	File Download Completion	File not downloaded	File fully downloaded
7	File Validity	Not confirmed	File is valid

Settings Parameters

Table 7 - Settings Parameters

Note

The internal structure of all sets of settings is similar to the structure of the set described, except for the initial address.

Note

Parameters marked with * are available both over MODBUS and WEB in the Wi-Fi setup mode.

Parameter	Range of values	Factory setting	Description	Address
Wi-Fi network
Static IP-address*	IP-address	192.168.0.111	If the dynamic addressing is switched off, IP-address of the device in Wi-Fi network is equal to this value	300 – 303
Subnetwork mask*	IP-mask	255.255.255.0	It is used only with static IP-address	304 – 307
Gateway*	IP-address	192.168.0.1	It is used only together with static IP-address for communication with other networks	308 – 311
Switch on the dynamic addressing with a help of DHCP*	0 – 1	1	0 – for addressing on Wi-Fi access point network, the specified values of the IP address, mask and gateway are used;	312
			1 – If DHCP server is available in the network, then IP address, mask and gateway are received from the server
Unused parameter	0	0	Should be 0 for compatibility	313
Switch on the use of server gateway DNS	0 – 1	1	0 – DNS of gateway is not used;	314
			1 – The gateway DNS is used to determine the IP addresses of other servers, if they are specified by host names
IP-address of DNS server	IP-address	8.8.8.8	It sets IP-address of a DNS server	315 – 318
IP-address of additional DNS server	IP-address	0.0.0.0	0.0.0.0 – it is not used	319 – 322
Unused parameter	0	0	Should be 0 for compatibility	323 – 339
SSID – Wi-Fi access point*	Character string		EM-482 is connected to the given access point. Up to 32 characters	340 – 371
Wi-Fi access point password*	Character string		Up to 24 characters	372 – 395
Unused parameter	0	0	Should be 0 for compatibility	396 – 449
Modbus TCP Server
TCP connection port for Modbus TCP	1 – 65535	502	It is used for external connection to EM-482 via Ethernet for exchange via Modbus TCP protocol	450
Disconnect inactive clients	0 – 1	1	0 – incoming TCP connection is kept regardless of the time between requests from the client;	451
			1 – disconnect clients that did not send requests for longer than a specified time
Max. request waiting time, s	0 – 600 000	90	Used if disconnection of inactive clients is selected	452 – 453
Unused parameter	0	0	Should be 0 for compatibility	454 - 456
Own Modbus-identifier of EM-482	0 – 247	111	0 – all queries are sent via Modbus to the Modbus network, the device registers are unavailable by Modbus;	457
			1 - 247 – the device responds Modbus queries with this Modbus identifier without forwarding them on
RS-485 network
Bit rate via RS-485, bit/sec*	75 – 230 400	9 600	It is used in case of data exchange between the devices via RS-485, the same value for the devices on the same RS-485 bus cable	458 – 459
Unused parameter	1	1	Should be 1 for compatibility	460
Byte format when transmitting via RS-485*	0 – 5	5	It is used in case of data exchange between the devices via RS-485. See Table 7.1 for formats.	461
Waiting time for starting the Modbus RTU response, ms	0 – 60 000	200	It is used for transmissions via RS-485 in Modbus RTU mode. After transmission of query, if the first byte of the response was not received within this time interval, the waiting for the response is terminated. The response is always waited for at least the silence time between frames	462
Enable ASCII exchange mode in Modbus network	0 – 1	0	Exchange mode via RS-485, the same value for all units on the same RS-485 bus cable.	463
			0 – RTU exchange mode (format: 1 start bit, 8 data bits, 2 stop-bits, parity bit, and stop bit or only 1 stop bit – total from 10 to11 bits);
			1 – ASCII exchange mode (format: 1 start bit, 7 data bits, 2 stop-bits or parity bit and stop bit - total is 10 bits). The non-standard byte formats (register 461, values 4 and 5) are not available in this case, format 3 (2 stop bits) is used instead
Response time for subsequent Modbus ASCII character, ms	0 – 60 000	1 000	It is used in case of data transfer via RS-485 in Modbus ASCII mode. If you receive a response, if the next byte of the response was not received within this time interval, then the response waiting is stopped. Waiting is always not less than the transmission time of one character (depends on the transmission speed)	464
Connection to the cloud server
Mode of connection to the cloud server*	0 – 1	1	0: connection to the server is not used;	465
			1: establish and maintain a connection to the data collection server
Cloud server connection port	0 – 65535	20502	The port to which the party is addressed, making connection between EM-482 and the server (see reg. 465)	466
Time of waiting for response from the cloud server, s	0 – 3 600	120	0 – the server silence time is not limited;	467
			1–3600 – max. time of server silence after which the connection will be stopped and must be remade again
Delay time before reconnecting to the cloud server, s	0 – 30 000	15	It is used when connecting to the server. After losing connection to the server, the reconnection will be performed after the specified waiting time	468
Unused parameter	0	0	Should be 0 for compatibility	469 - 473
Enable setting the server address with a text string	0 – 1	1	This is used when connecting to the server.	469
			0: the connection is made to a server with a fixed IP address specified in registers 470-473;
			1: the connection is made to the server with the name specified in registers 474-509
Server’s IP address	IP address	0.0.0.0	This is used when connecting to the server, if setting the server’s address with a text string is disabled. IP address of a remote server, with which the connection is maintained	470 – 473
Cloud server address	Character string	modbus.overvis.com	It is used when connecting to the server, if the server address setting is turned on with text string. Address of the remote server with which the connection is supported.	474 - 509
			The string of up to 36 characters can be indicated as address. This string should not have any spaces
Protection
Password for setup mode access	Character string	11111	It is used to access the configuration mode. The string of 5 to 10 characters in length can be indicated as password. This string should not have any spaces	510 – 519
Unused parameter	0	0	Should be 0 for compatibility	520 – 549
Password for writing permission via Modbus to the other devices	Character string		It is used to access devices connected to the EM-482, to request write or control functions that can change the status of these devices. The string up to 10 characters in length can be specified as password. This string should not have any spaces	550 – 559
Password for reading permission via Modbus	Character string		It is used to access devices connected to the EM-482, to request read functions, or to access the EM-482 registers, except for registers of version, password, mode and flags. The string up to 10 characters in length can be indicated as password. This string should not have any spaces	560 – 569
Unused parameter	0	0	Should be 0 for compatibility	570 – 571
Enable the protection mode against writing via Modbus	0 – 1	0	0 – Protection against recording is regulated with help of other parameters (password) or deactivated;	572
			1 - Blocking of any queries for functions, excepting functions of Modbus 1, 2, 3, 4, 7, 17, 20
Enable the protection mode against reading via Modbus	0 – 1	0	0 – Protection against reading is regulated with help of other parameters (password) or deactivated;	573
			1 – Blocking of queries for functions of Modbus 1, 2, 3, 4, 7, 17, 20, excepting reading using function 3 of registers of version, mode and tabs
Unused parameter	0	0	Should be 0 for compatibility	574
Miscellaneous
Unused parameter	0	0	Should be 0 for compatibility	575 - 629
Enable automatic restart of the Product	0 – 1	1	0: periodic restart is disabled;	630
			1: the Product is restarted after a specified period of time
Restart time, min	5 – 7 200	120	Used when automatic restart is enabled.	631
Enable restart mode automatically only in the absence of connections	0 – 1	1	This is used if automatic restart is enabled.	632
			0: the Product is restarted after a specified period of time since the start;
			1: the Product is restarted after a specified period of time since the last MODBUS transmission
Modbus exception code generated when access is denied	0 – 255	1	0 – if the access to Modbus registers is denied, the response to the client is not returned;	633
			1 – 255 – if you deny access to the client who sent the request, this exception code is returned
Modbus exception code generated when there is no response	0 – 255	11	0 – if there is no response from the addressee (Gateway Timeout), the response to the client is not returned;	634
			1 - 255 – if there is no response from the request recipient, this exception code is returned to the client
Unused parameter	0	0	Should be 0 for compatibility	635
Modbus exception code generated if there is no connection to query addressee	0 – 255	10	0 – If there is no connection to the query addressee (Gateway Path Unavailable), response is not returned to the client;	636
			1 – 255 – if there is no connection to the query addressee, this exception code is returned to the client
RS-485 transmission mode	0 – 1	0	0 – Master mode (Modbus Master): RS-485 is used to send queries;	637
			1 – Slave mode (Modbus Slave): RS-485 is used to receive queries from additional client;
First Modbus-identifier of RS-485	1 – 255	1	Two parameters define a range of Modbus identifiers used for RS-485.	638
			In the master mode the queries with addresses in this range (and also the broadcast ones with address 0) are sent via RS-485.
			In the slave mode the queries with addresses in this range (and also the broadcast ones and the queries to EMC-482 address) are received via RS-485
Last Modbus-identifier of RS-485	1 – 255	255	same as above	639
Connection to the remote Modbus TCP server
IP-address of the remote server*	IP-address	192.168.0.112	It is used with enabled redirection of queries to a remote Modbus TCP server. IP-address of the remote server wherewith connection is maintained	640 – 643
Port of the remote server connection	0 – 65535	502	Port of the remote server to which the TCP connection will be established	644
Time to wait for response from remote server, ms	0 – 60 000	1 000	It is used during redirection of queries to the remote server. After the query transfer, if the correct response has failed to be received within this time interval, response waiting is stopped	645
Standby time to repeated connection to the remote server, s	0 – 240	20	It is used during redirection of queries to the remote server. After connection with the server is lost, the repeated connection will be performed after preset standby time	646
Remote server connection mode*	0 – 1	0	0: remote MODBUS TCP server is not used;	647
			1: the connection to the remote MODBUS TCP server is established and automatically maintained
First Modbus-identifier of the remote server	1 – 255	1	It is used during redirection of queries to the remote server.	648
			Two parameters define the range of Modbus identifiers used on the remote server.
			Queries with addresses in this range (and also the broadcast ones with address 0) are sent to the remote Modbus TCP server
Last Modbus-identifier of the remote server	1 – 255	255	same as above	649
Unused parameter	0	0	Should be 0 for compatibility	650 – 729
Wi-Fi services
Period of search for the best Wi-Fi hotspot	0 − 72	4	0: do not search for access points with a better signal and don’t switch between them until the connection is lost; Other values: the number of hours until the search for the access point of the same name with better signal	730
Unused parameter	0	0	Should be 0 for compatibility	731 – 739
Product Name	Character string		Name to distinguish products from each other	740 – 779
			The string of up to 36 characters can be indicated as address.
Unused parameter	0	0	Should be 0 for compatibility	780 – 799
User’s Settings
User’s settings and saved values	0–65535	0	They can be used for storing any product identification data, or filled in by MODBUS clients for storing and transmitting data to the server	5250 – 5499

Table 7.1 - RS-485 Byte Formats (Register 461)

Value	Format	Description
0	EVEN	1 parity bit, 1 stop bit
1	ODD	1 parity bit, 1 stop bit
2	0 (SPACE)	1 zero bit, 1 stop bit
3	1 (MARK)	1 unit bit, 1 stop bit (similar to 2 stop bits)
4	ABSENT	No parity bit, 1 stop bit
5	AUTO-STOP	No parity bit, 2 stop bits (tx), 1 stop bit (rx)

FAQ

Q: What is the default Modbus TCP port and device address?

A: EM-482 listens on TCP port 502 (configurable in register 450) and uses Modbus address 111 by default (configurable in register 457). The current IP address can be usually checked at the network router which provides the Wi-Fi access point for EM-482.

Q: How do I enter Setup Mode to change configuration?

A: Write the password (found on the device label) to registers 100-119. If correct, register 121 will read 1 (Setup Mode). You can then modify settings in the Changeable Settings registers (300-799).

Q: How do I save my configuration changes?

A: Write command 2 to register 120 to save (then restart EM-482 for the changes to take effect), or 4 to save and apply immediately (only for Modbus and user’s settings). Write 9 to cancel unsaved changes.

Q: I have saved the new settings, how do I restart EM-482 remotely?

A: Write command 1 to register 120 to restart. EM-482 will reboot and usually be available again in half a minute. You may need to reconnect then.

Q: How do I configure RS-485 communication parameters?

A: Key registers are:

• 458-459: Baud rate (default 9600)
• 461: Byte format/parity (see Table 7.1)
• 463: Protocol mode (0=Modbus RTU, 1=Modbus ASCII)
• 637: Transmission mode (0=Master, 1=Slave)

Q: What is the difference between Master and Slave RS-485 modes?

A: In Modbus Master mode (default), EM-482 sends queries to RS-485 devices (these queries come from Modbus TCP clients via Wi-Fi). In Modbus Slave mode, EM-482 receives queries from an external Modbus Master on RS-485 (these queries usually are intended for remote Modbus TCP server accessible via Wi-Fi). Use Slave mode when EM-482 should act as a slave device on an existing RS-485 network.

**Q: I have configured RS-485 and set EM-482 modbus device ID parameter to match my RS-485 device address. But I still get errors like Illegal address.

A: This can happen because EM-482 (configured this way) reads its own Modbus registers instead of redirecting the requests to your RS-485 device. Do not set EM-482 own Modbus ID in the Modbus TCP Server parameters to any of your devices addresses. However, reading registers of any device with ID other than this one (which is 111 by default) should work.

Q: Can I connect the RS-485 device if its protocol differs from Modbus?

A: No, the EM-482 supports only Modbus protocol transfers.

Q: Can I connect EM-482 to multiple remote Modbus TCP servers?

A: EM-482 supports connection to a single remote TCP server. If this server is itself a EM-482 converter, they can be configured as a chain, with each one connecting to the next EM-482 IP address. However, the delays are increased with the chain length. To connect several of the other Modbus TCP devices, a converter supporting multiple remote servers can be used (one from the EM-48x or MC-25x series, e.g. EM-483). Configure each remote connection in devices’s registers 640-649. The main parameters are the connection mode and the server IP address. Also, set Modbus ID range for each remote server to avoid extra traffic and delays.

Q: How do I reset the device to factory defaults?

A: Enter Setup Mode by writing the password, then write command 444 to register 120. All settings will be reset to factory defaults, including passwords. Restart EM-482 for the changes to take effect.

Q: How do I check the current firmware version?

A: Read register 1 for the firmware version number.

Need Help?

For technical support and assistance:

• Email: support@overvis.com
• Support portal: www.overvis.com/support