Modbus® Serial
to
Modbus® TCP/IP
Gateway
Instruction Manual
GTW-MB-MBTCP
Table of Contents
1. General Description....................................................................................................... 3
2. Specifications ................................................................................................................ 4
2.1 Electrical ........................................................................................................... 4
2.2 Physical ............................................................................................................ 4
3. Installation ..................................................................................................................... 5
3.1 Wiring Guidelines ............................................................................................. 5
3.2 Signal Connections........................................................................................... 5
4. Description of Features ................................................................................................. 6
4.1 Hardware Settings ............................................................................................ 6
4.2 LEDs ................................................................................................................. 6
4.3 Software Settings.............................................................................................. 7
5. Adjustment Procedure................................................................................................. 16
6. Prints ........................................................................................................................... 18
C14068 GTW-MB-MBTCP Assembly................................................................... 18
7. Standard Terms & Conditions of Sale ......................................................................... 19
List of Figures
Figure 1: Physical Dimensions .......................................................................................... 4
Figure 2: General Connections.......................................................................................... 5
Figure 3: Network Settings ................................................................................................ 7
Figure 4: Server Settings ................................................................................................... 8
Figure 5: Serial Settings .................................................................................................. 10
Figure 6: Modbus/TCP Connection Settings ................................................................... 12
Figure 7: Configurable Pin Settings................................................................................. 15
Figure 8: Example RS422 Four Wire Connections.......................................................... 16
Figure 9: Example RS485 Four Wire Connections.......................................................... 16
Figure 10: Example RS485 Two Wire Connections ........................................................ 17
List of Tables
Table 1: J3 Settings........................................................................................................... 6
Table 2: Connection LED .................................................................................................. 6
Table 3: Activity LED ......................................................................................................... 6
Table 4: J3 Settings......................................................................................................... 16
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General Description
Model GTW-MB-MBTCP is designed to provide a network gateway between a Modbus®
(RTU or ASCII) serial network and a Modbus® TCP/IP network. This unit will convert
any existing serial Modbus RTU unit to a Modbus TCP/IP unit.
The gateway can interface with 4 wire RS422, and 2 or 4 wire RS485 networks. The
module also has a provision for a terminating resistor if desired.
Features
• 10/100M Ethernet
• DHCP or Static IP Address
• Web Page Configuration
• Modbus RTU or ASCII
• Selectable Baud Rate, Stop Bits, Parity
• RS422 (4 wire), RS485 (2 or 4 wire modes)
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Specifications
2.1 Electrical
D.C. Power Input
• 24 VDC ±10%, 60mA max, internally fused
Network Interface
• RJ45
• 10/100M Ethernet
Serial Interface
• Terminal Blocks
• RS422/RS485
• 115Kbaud max
Temperature Range
• 0-55º C
2.2 Physical
Figure 1: Physical Dimensions
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Installation
3.1 Wiring Guidelines
To prevent electrical interference and to minimize start-up problems, adhere to the
following guidelines:
Use fully insulated and shielded cable for all signal wiring. The shield should be
connected to circuit common at one end only. The other end of the shield should be
clipped and insulated to prevent the possibility of accidental grounding.
Signal level wiring such as listed above should be routed separately from high level
power wiring (such as the A.C. line, motor, operator control, and relay control
wiring). When these two types of wire must cross, they should cross at right angles
to each other.
Any relay, contactor, starter, solenoid or other electro-mechanical device located in
close proximity to or on the same line supply as the GTW-MB-MBTCP should have
a transient suppression device such as an MOV or R-C snubber connected in
parallel with its coil. The suppressor should have short leads and be connected as
close to the coil as possible.
3.2 Signal Connections
Figure 2: General Connections
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Description of Features
4.1 Hardware Settings
The following are hardware selectable settings. The jumpers are accessible by
squeezing the sides near the top and removing the enclosure bottom.
JUMPERS J1/J2 Biasing
On some RS485 networks, it is necessary to bias the bus for proper operation.
This biasing can be applied by jumpers J1 and J2. Biasing is typically not required
on RS422 networks. On 485 networks, typically only one device on the network
should provide the biasing.
JUMPERS J3 Echo
When J3 is set to OFF, the RS422/485 receiver is disabled during a serial
transmission. When set to ON, the receiver is always enabled. Refer to the table
below for typical jumper settings based on the serial operating mode.
Mode J3 Echo
RS422 (4 wire) ON
RS485 (4 wire) ON
RS485 (2 wire) OFF
Table 1: J3 Settings
TERMINATOR
It is recommended to install a terminating resistor at the beginning and end of the
RS422/485 network. Placing a jumper between terminals 4 & 5 includes a 120 ohm
terminating resistor across the units serial receiver.
4.2 LEDs
Top LED State
Solid Amber 10BASE-T
Solid Green 100BASE-T
Off No Connection
Table 2: Connection LED
Bottom LED State
Blinking Amber Half Duplex Activity
Blinking Green Full Duplex Activity
Table 3: Activity LED
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4.3 Software Settings
The following are software selectable settings that are available via the web
interface. Please refer to Adjustment Procedure on page 16 for instructions on how
to access the web interface.
When changes are made on a page, the OK button must be clicked and then Apply
Settings (on the left) must then be clicked. This must be done for each page.
Multiple pages cannot be edited and then applied.
NETWORK SETTINGS
Figure 3: Network Settings
Obtain an IP Address Automatically
Select this option if you want the IP address to be assigned automatically via
BOOTP, DHCP, or AutoIP methods.
DHCP Host Name
Enter the desired host name for the GTW-MB unit. This is optional.
Use the following IP Configuration
Select this option if you want to manually assign the network settings. When
this option is selected, you must enter the appropriate IP Address, Subnet
Mask, and Default Gateway settings.
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SEVER SETTINGS
Figure 4: Server Settings
Enhanced Password
When set to enabled, passwords up to 16 bytes in length can be created.
When disabled, passwords up to 4 bytes in length must be used.
Telnet/Web Manager Password
Enter the password for the Telnet configuration and Web Manager access.
Retype Password
Re-enter the password required for Telnet configuration and Web Manager
access.
ARP Cache Timeout
When the unit communicates with another device on the network, it adds an
entry into its ARP table. ARP Cache timeout defines the number of seconds (1-
600) before it refreshes this table.
TCP Keepalive
This setting defines how many seconds the unit waits during an inactive
connection before checking its status. If the unit does not receive a response, it
drops that connection. Enter a value between 0 and 60 seconds. 0 disables
keepalive. The default setting is 45.
Monitor Mode @ Bootup
Select Disable to disable entry into the monitor mode using the 'yyy' or 'xx1' key
sequence at startup. This field prevents the unit from entering monitor mode by
interpreting the stream of characters that are received during the device server's
initialization at startup.
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HTTP Server Port
This option allows the configuration of the web server port number. The valid
range is 1-65535. The default port is 80.
MTU Size
The Maximum Transmission Unit (MTU) is the largest physical packet size a
network can transmit for TCP and UDP. Enter between 512 and 1400 bytes.
The default is 1400 bytes.
TCP Re-transmission Timeout
The desired TCP re-transmission timeout value. If the ACK is not received for a
packet sent from the device, then the unit will retransmit the data. The valid
range is 500-4000ms. The default is 500ms.
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SERIAL SETTINGS
Figure 5: Serial Settings
Interface
Select the type of serial interface that will be used. Valid selections are
RS422/RS485 4 WIRE and RS485 2 Wire. Do not select RS232.
Baud Rate
The unit and all attached serial devices must agree on a speed or baud rate to
use for the serial connection. Valid baud rates are 300, 600, 1200, 2400, 4800,
9600 (default), 19200, 38400, 57600, 115200.
Data Bits
Indicates the number of bits in a transmitted data package. The default is 8.
Parity
Checks for the parity bit. The default is None.
Stop Bits
The stop bit follows the data and parity bits in serial communication. It indicates
the end of transmission. The default is 1.
Flow Control Out
This setting is not used.
Modem Control Out
This setting is not used.
Protocol
Select the desired Modbus protocol to be used: RTU (binary) or ASCII. Default
is RTU.
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Tx Delay after Rx
This feature inserts a delay between the Modbus/TCP master requests. The first
request is sent out of the serial port of the device to the Modbus slave. When
the slave responds, it triggers this timer. After the specified delay is reached, the
next master request is allowed to pass through the serial port, and the timer is
reset. This feature is particularly useful when using RS485 2-wired serial
protocol. The delay gives ample time for the RS485 slave devices to turn their
transmitters off and their receivers back on. Default is 0ms.
Character Timeout
This sets the timeout between characters received. Official Modbus/RTU
defines a 3.5 character time-out, but complex devices have various interrupts
that can cause 5 to 10 character “pauses” during transmission. A safe value for
general use with Modbus is 50ms. Note: Setting this value lower than 50ms will
not improve performance and may even make performance worse. Default is
50ms.
Message Timeout
This sets the timeout for a response from a connected slave both serially and by
TCP/IP. Default is 5000ms.
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MODBUS/TCP CONNECTION SETTINGS
Figure 6: Modbus/TCP Connection Settings
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Connect Protocol
When Modbus/TCP Server attached to slave(s) is selected, the unit functions as
a Modbus/TCP server. The attached serial devices function as Modbus slaves.
When Modbus/TCP Client attached to master is selected, the unit functions as
a Modbus/TCP client. The attached serial device is a Modbus master.
Modbus/TCP Port
Defines the Modbus port. Default is 502.
Fixed Slave Address
Modbus/TCP includes a Unit ID field, which is used to address multiple Modbus
slaves at a single IP address. Unfortunately, some first generation software
drivers assumed a single slave at each IP and always set the Unit ID field to 0.
This can sometimes causes problems because the device requires the Unit ID
for the Modbus/RTU “Slave Address.” To support these older applications, the
device allows you to force a fixed address. However, be aware that this restricts
you to a single serial slave device per unit. Setting this value to 0 causes the
device to use the Modbus/TCP Unit ID as received. Setting it to any other
address causes the device to always use the set value as a fixed address.
Queue Multiple Modbus/TCP Requests
While the Modbus/TCP standard specification requires Modbus/TCP
masters/clients to only issue one poll at a time, the full-duplex flow-controlled
nature of TCP/IP allows them to issue more than one at a time, and the TCP
socket will buffer them. When set to Yes, the device will fetch the requests one
at a time and answer each in turn. This is the safest default setting – only
change this if you are having problems. Setting this to No causes the device to
always fetch the newest request from the TCP buffer – all older requests are
discarded. This allows a Modbus/TCP master/client to retry old requests without
risking building up a stale queue of waiting requests. Default is Yes.
Allow Modbus Broadcast
Enables/disables the serial Modbus broadcast function.
Use Bridge Error Codes (0AH/0BH)
Traditional serial Modbus uses silence to signal some errors. While this works
well with direct serial lines, it causes serious problems on a TCP/IP wide-areanetwork where delays are not so predictable. See for a full discussion. Setting
this parameter to No causes the device to behave like a traditional Modbus
serial slave – it answers timeouts, unconfigured slave addresses, and CRC
errors with silence. Setting this to Yes causes the device to return 1 of 2 new
exception codes defined in Modbus/TCP. Default is Yes.
Swap 4x/0x access to get 3x/1x
This setting will convert holding register (4x) data reads to input register (3x)
data reads. It also converts coil (0x) reads to contact data (1x) reads. This
feature is useful for Modicon I/O scanners that only support reads of holding
registers and coils. This feature works in conjuiction with the offsets defined
below. Default setting is No.
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Swap Holding Reg (4x) access to Input Reg (3x) after offset
Allows the above swap feature only if the request is above an offset. Example:
read of 401023 maps to 300023 if you enter 1000). Default is 0.
Swap Coil Status (0x) access to Input Status (1x) after offset
Allows the above swap feature only if the request is above an offset. Example:
read of 001023 maps to 100023 if you enter 1000). Default is 0.
Preset Automated Scan Table (optional)
This section is only utilized when the Modbus/TCP Server attached to slave(s)
serial protocol is selected. The Preset Automated Scan Table contains optional
settings that direct the unit to automatically access Modbus registers on the
slave(s). This is useful when multiple Modbus/TCP clients are polling the same
group of “interesting” registers. The scan allows the registers to be pre-fetched
one time and then delivered without delay to multiple requesting clients. The
auto scan operation also allows the TCP connection status and the network
settings to be written to the connected slave’s registers
Unit Id
The network address of the serial Modbus device.
Register Type
Selects the type of register:
• Reads
Holding Register (4x)
Input Register (3x)
Input Status (1x)
Coil Status (0x)
• Writes
TCP Status (0x)
IP Config (4x)
IP + Netmask (4x)
IP + Net + Gateway (4x)
Offset
The starting offset of the Modbus register(s). Example: Input register offset of
10 yields address 3x00010.
Count
The number of registers to be accessed. Range is 1 to 124.
Frequency
The time in milliseconds between accesses. Range is 50-65000ms.
Unit ID to IP Address Mapping
This section is only utilized when the Modbus/TCP Client attached to master
serial protocol is selected. Since serial Modbus network uses 8-bit slave
addresses and a TCP/IP network requires 32-bit IP addresses, the unit uses this
table to map an 8-bit address into an IP/Unit ID combination. The 8-bit address
is used to both select the desired IP and as the Unit ID sent. The table holds 8
entries, and any Modbus slave
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address not found in the table returns an exception response to the master (if
enabled).
Start Id / End Id
Enter a range of 8 bit Modbus addresses. Any Modbus packet that falls within
this range is forwarded to the Host Address.
Host Address
This is the IP Address of the remote Modbus/TCP slave.
Close Idle TCP Sockets after
Sockets are opened as required. Entering a 0 holds a single socket open to the
last remote Modbus/TCP slave accessed. Otherwise enter values 3 to 60 to
automatically close the last socket after 3 to 60 seconds of idle time.
Redundant Entry Retries after
Enter the time in seconds for redundant entry retries or set to 0 to disable the
feature.
CONFIGURABLE PINS
Figure 7: Configurable Pin Settings
No adjustment should be made to these settings. They should be left at their
defaults as shown above.
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Adjustment Procedure
Step 1: Determine serial interface
1. Determine the type of serial interface that will be used: RS422 (4 wire),
RS485 (4 wire), or RS485 (2 wire). Most often, this is determined by the
device(s) that will be connected to the gateway. Place Jumper J3
accordingly
Mode J3 Echo
RS422 (4 wire) ON
RS485 (4 wire) ON
RS485 (2 wire) OFF
Table 4: J3 Settings
2. Place Jumpers J1 & J2 to OFF is biasing is not needed. If unsure, place in
Step 2: Connections
the ON position.
1. Make connections per one of the examples below.
Figure 8: Example RS422 Four Wire Connections
Figure 9: Example RS485 Four Wire Connections
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Figure 10: Example RS485 Two Wire Connections
Step 3: Initial Configuration
1. Apply power to the module.
2. If a DHCP server exists on the network, it should assign the unit an IP
address. If this address is unknown or no DHCP server exists, the Lantronix
DeviceInstaller utility must be used to 'find' and configure the unit's network
settings. Download and install the DeviceInstaller utility from
www.carotron.com.
3. When the DeviceInstaller utility initially runs, it searches the network for
devices and displays the IP address when found. If this address is sufficient,
proceed to Step 4. If you wish to change the IP address, expand the tree
structure in the left pane. Select the device in the right pane. Click on the
Assign IP button in the toolbar to change the network settings.
Step 4: Web Interface
1. Once the IP address is known, simply open a web browser and enter the IP
address (i.e. 192.168.0.5) in the address bar. If a username and password
have been configured, enter those when prompted. Otherwise, leave the
username and password fields blank.
2. Select Serial Settings from the menu on the left.
3. Set the Interface to the desired option. This setting should match the jumper
J3 selection that was made in Step 1.
4. Set the Baud Rate, Data Bits, Parity, & Stop Bits. These settings should
match the serial settings in the connected device(s).
5. Set the desired protocol: RTU or ASCII. For Carotron serial devices, select
RTU.
6. Click OK
7. Click Apply Settings from the menu on left. Device will re-boot.
8. Additional settings may also be set via the web interface. Refer to section
4.3 Software Settings on page 7 for additional details.
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Prints
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Standard Terms &
Conditions of Sale
1. General
The Standard Terms and Conditions of Sale of Carotron, Inc. (hereinafter
called “Company”) are set forth as follows in order to give the Company
and the Purchaser a clear understanding thereof. No additional or different
terms and conditions of sale by the Company shall be binding upon the
Company unless they are expressly consented to by the Company in
writing. The acceptance by the Company of any order of the Purchaser is
expressly conditioned upon the Purchaser’s agreement to said Standard
Terms and Conditions. The acceptance or acknowledgement, written, oral,
by conduct or otherwise, by the Company of the Purchaser’s order shall
not constitute written consent by the Company to addition to or change in
said Standard Terms and Conditions.
2. Prices
Prices, discounts, allowances, services and commissions are subject to
change without notice. Prices shown on any Company published price list
and other published literature issued by the Company are not offers to sell
and are subject to express confirmation by written quotation and
acknowledgement. All orders of the Purchaser are subject to acceptance,
which shall not be effective unless made in writing by an authorized
Company representative at its office in Heath Springs, S.C. The Company
may refuse to accept any order for any reason whatsoever without
incurring any liability to the Purchaser. The Company reserves the right to
correct clerical and stenographic errors at any time.
3. Shipping dates
Quotation of a shipping date by the Company is based on conditions at
the date upon which the quotation is made. Any such shipping date is
subject to change occasioned by agreements entered into previous to the
Company’s acceptance of the Purchaser’s order, governmental priorities,
strikes, riots, fires, the elements, explosion, war, embargoes, epidemics,
quarantines, acts of God, labor troubles, delays of vendors or of
transportation, inability to obtain raw materials, containers or
transportation or manufacturing facilities or any other cause beyond the
reasonable control of the Company. In no event shall the Company be
liable for consequential damages for failure to meet any shipping date
resulting from any of the above causes or any other cause.
In the event of any delay in the Purchaser’s accepting shipment of
products or parts in accordance with scheduled shipping dates, which
delay has been requested by the Purchaser, or any such delay which has
been caused by lack of shipping instructions, the Company shall store all
products and parts involved at the Purchaser’s risk and expense and shall
invoice the Purchaser for the full contract price of such products and parts
on the date scheduled for shipment or on the date on which the same is
ready for delivery, whichever occurs later.
4. Warranty
The Company warrants to the Purchaser that products manufactured or
parts repaired by the Company, will be free, under normal use and
maintenance, from defects in material and workmanship for a period of
one (1) year after the shipment date from the Company’s factory to the
Purchaser. The Company makes no warranty concerning products
manufactured by other parties.
As the Purchaser’s sole and exclusive remedy under said warranty in
regard to such products and parts, including but not limited to remedy for
consequential damages, the Company will at its option, repair or replace
without charge any product manufactured or part repaired by it, which is
found to the Company’s satisfaction to be so defective; provided, however,
that (a) the product or part involved is returned to the Company at the
location designated by the Company, transportation charges prepaid by
the Purchaser; or (b) at the Company’s option the product or part will be
repaired or replaced in the Purchaser’s plant; and also provided that Cc)
the Company is notified of the defect within one (1) year after the
shipment date from the Company’s factory of the product or part so
involved.
The Company warrants to the Purchaser that any system engineered by it
and started up under the supervision of an authorized Company
representative will, if properly installed, operated and maintained, perform
in compliance with such system’s written specifications for a period of one
(1) year from the date of shipment of such system.
As the Purchaser’s sole and exclusive remedy under said warrant in
regard to such systems, including but not limited to remedy for
consequential damages, the Company will, at its option, cause, without
charges any such system to so perform, which system is found to the
Company’s satisfaction to have failed to so perform, or refund to the
Purchaser the purchase price paid by the Purchaser to the Company in
regard thereto; provided, however, that (a) Company and its representatives are permitted to inspect and work upon the system involved during
reasonable hours, and (b) the Company is notified of the failure within one
(1) year after date of shipment of the system so involved.
The warranties hereunder of the Company specifically exclude and do not
apply to the following:
a. Products and parts damaged or abused in shipment without
fault of the Company.
b. Defects and failures due to operation, either intentional or
otherwise, (l) above or beyond rated capacities, (2) in connection
with equipment not recommended by the Company, or (3) in an
otherwise improper manner.
c. Defects and failures due to misapplication, abuse, improper
installation or abnormal conditions of temperature, humidity,
abrasives, dirt or corrosive matter.
d. Products, parts and systems which have been in any way
tampered with or altered by any party other than an authorized
Company representative.
e. Products, parts and systems designed by the Purchaser.
f. Any party other than the Purchaser.
The Company makes no other warranties or representation, expressed or
implied, of merchantability and of fitness for a particular purpose, in regard
to products manufactured, parts repaired and systems engineered by it.
5. Terms of payment
Standard terms of payment are net thirty (30) days from date of the
Company invoice. For invoice purposed, delivery shall be deemed to be
complete at the time the products, parts and systems are shipped from the
Company and shall not be conditioned upon the start up thereof. Amounts
past due are subject to a service charge of 1.5% per month or fraction
thereof.
6. Order cancellation
Any cancellation by the Purchaser of any order or contract between the
Company and the Purchaser must be made in writing and receive written
approval of an authorized Company representative at its office in Heath
Springs, S.C. In the event of any cancellation of an order by either party,
the Purchaser shall pay to the Company the reasonable costs, expenses,
damages and loss of profit of the Company incurred there by, including
but not limited to engineering expenses and expenses caused by
commitments to the suppliers of the Company’s subcontractors, as
determined by the Company.
7. Changes
The Purchaser may, from time to time, but only with the written consent of
an authorized Company representative, make a change in specifications
to products, parts or systems covered by a purchase order accepted by
the company. In the event of any such changes, the Company shall be
entitled to revise its price and delivery schedule under such order.
8. Returned material
If the Purchaser desires to return any product or part, written authorization
thereof must first be obtained from the Company which will advise the
Purchaser of the credit to be allowed and restocking charges to be paid in
regard to such return. No product or part shall be returned to the Company
without a ”RETURNTAG” attached thereon which has been issued by the
Company.
9. Packing
Published prices and quotations include the Company’s standard packing
for domestic shipment. Additional expenses for special packing or
overseas shipments shall be paid by the Purchaser. If the Purchaser does
not specify packing or accepts parts unpacked, no allowance will be made
to the Purchaser in lieu of packing.
10. Standard transportation policy
Unless expressly provided in writing to the contrary, products, parts and
systems are sold f.o.b. first point of shipment. Partial shipments shall be
permitted, and the Company may invoice each shipment separately.
Claims for non-delivery of products, parts and systems, and for damages
thereto must be filed with the carrier by the Purchaser. The Company’s
responsibility therefor shall cease when the carrier signs for and accepts
the shipment.
19
Issued 0
5-07-
201
8
3204 Rocky River Road
Heath Springs, SC 29058
Phone: 803.286.8614
Fax: 803.286.6063
Email: saleserv@carotron.com
Web: www.carotron.com
MAN1062-00 Rev. A
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