MTL WMO-400S User manual
WMO-400S
Radio Modem
User Guide
INM WMO400S
WMO-400S Radio Modem Module
Page 2 Jul 2010
Thank you for your selection of the WMO-400S radio modem.
We trust it will give you many years of valuable service.
ATTENTION!
Incorrect termination of supply wires may
cause internal damage and will void warranty.
To ensure your WMO-400S enjoys a long life,
double check ALL your connections
with the user’s manual
before turning on the power.
Important Regulatory Information
FCC
Part 15 – This device has been tested and found to comply with the limits for a Class
B digital device, pursuant to Part15 of the FCC rules (Code of Federal
Regulations 47CFR Part 15). Operation is subject to the condition that this
device does not cause harmful interference.
Part 90 – This device has been type accepted for operation by the FCC in accordance
with Part90 of the FCC rules (47CFR Part 90). See the label on the unit for
the specific FCC ID and any other certification designations.
Note This device should only be connected to PCs that are covered by either a
FCC DoC or are FCC certified.
Industry Canada
RSS-119 - This device has been type accepted for operation by Industry Canada in
accordance with RSS-119 of the Industry Canada rules. See the label on the
unit for the specific Industry Canada certification number and any other
certification designations.
Notice
Any changes or modifications not expressly approved by MTL
Technologies P/L could void the user’s authority to operate this equipment.
To operate this equipment legally the user must obtain a radio operating
license from the government agency. This is done so the government can
coordinate radio users in order to minimize interference.
User Manual
INM WMO400S_v3 03_2.doc Page 3
How to Use This Manual
To receive the maximum benefit from your WMO-400S product, please read the
Introduction, Installation and Configuration chapters of this manual
thoroughly before putting the WMO-400S to work.
Chapter Four Specifications details the features of the product and lists the
standards to which the product is approved.
Chapter Five Troubleshooting will help if your system has problems and
Chapter Seven specifies the Warranty and Service conditions.
The foldout sheet WMO-400S Installation Guide is an installation drawing
appropriate for most applications.
WARNING
1. To avoid the risk of electrocution, the antenna, antenna cable, and all
terminals of the WMO-400S module should be electrically protected. To
provide maximum surge and lightning protection, the module should be
connected to a suitable earth and the antenna, antenna cable, and the
module should be installed as recommended in the Installation Guide.
2. To avoid accidents during maintenance or adjustment of remotely
controlled equipment, all equipment should be first disconnected from the
WMO-400S module during these adjustments. Equipment should carry
clear markings to indicate remote or automatic operation. eg. "This
equipment is remotely controlled and may start without warning. Isolate
at the switchboard before attempting adjustments."
3. The WMO-400S module is not suitable for use in explosive environments
without additional protection.
4. All antenna installation and servicing should be done by qualified personal
only. When installing or working near the antenna it is important to
ensure that the transmitter is not operating, ensure the transmitter is
disabled.
5. The antenna can have very high RF radiating fields and must be installed
so that under normal operating conditions that a person cannot approach
within 2.3 metres (7.5 feet) of the antenna. See chapter 2 for antenna
installation guidelines.
WMO-400S Radio Modem Module
Page 4 Jul 2010
CONTENTS
WARNING............................................................................................................................... 3
CHAPTER ONEINTRODUCTION .................................................................................. 7
1.1GENERAL................................................................................................................. 7
1.1.1Basic Operation ......................................................................................................... 8
1.1.2Operating Modes ....................................................................................................... 8
1.1.3Repeater Functionality............................................................................................... 9
1.1.4Hot Redundant Standby............................................................................................. 9
1.2UNACKNOWLEDGED MODE ..................................................................................... 9
1.3ACKNOWLEDGED MODE........................................................................................ 10
1.4SECURITY ENCRYPTION......................................................................................... 13
1.5SERIAL AND RADIO DATA...................................................................................... 13
1.5.1PLC-Mode............................................................................................................... 14
1.5.2Character Type ........................................................................................................ 14
1.5.3Serial Data Rate....................................................................................................... 15
1.5.4Radio Data Rate....................................................................................................... 15
1.5.5Radio Message......................................................................................................... 15
1.6ADDRESSING.......................................................................................................... 16
1.6.1Multiple Device Connectivity (MDC)..................................................................... 17
1.7OPTIMUM PATH ROUTING...................................................................................... 17
1.8DUTY CYCLE LIMITING ......................................................................................... 18
1.9WHAT OPERATING MODE TO USE ?....................................................................... 18
1.9.1Unacknowledged or Acknowledged mode?............................................................ 18
1.9.2Error Check ............................................................................................................. 19
CHAPTER TWOINSTALLATION.................................................................... 20
2.1GENERAL............................................................................................................... 20
2.2ANTENNA INSTALLATION ...................................................................................... 20
2.2.13dB/6dB Collinear antenna. .................................................................................... 22
2.2.2Yagi antennas. ......................................................................................................... 23
2.3POWER SUPPLY...................................................................................................... 23
2.4SERIAL CONNECTIONS........................................................................................... 25
2.4.1 RS232 Serial Port ................................................................................................ 25
2.4.2 RS232 Configuration Port................................................................................... 26
2.4.3 RS485 Serial Port ................................................................................................ 26
2.5DISCRETE I/O POINT.............................................................................................. 27
2.5.1 Using the Discrete I/O as an Output.................................................................... 27
2.5.1 Using the Discrete I/O point as an Input............................................................. 27
2.6DUAL REDUNDANT INSTALLATION........................................................................ 28
CHAPTER THREECONFIGURATION........................................................................ 30
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INM WMO400S_v3 03_2.doc Page 5
3.1BEFORE CONFIGURING .......................................................................................... 30
3.1.1Addressing............................................................................................................... 30
3.1.2Command Mode...................................................................................................... 31
3.2DEFAULT CONFIGURATION.................................................................................... 31
3.3CONFIGURATION PROGRAM................................................................................... 31
3.3.1Reading and Configuring a module......................................................................... 32
3.4REMOTE CONFIGURATION AND DIAGNOSTICS ....................................................... 34
3.5UNACKNOWLEDGED MODE ................................................................................... 35
3.5.1RS-485 Port ............................................................................................................. 35
3.5.2RS-232 Port ............................................................................................................. 36
3.5.3 Unacknowledged mode Repeaters ...................................................................... 37
3.5.4 Multiple Transmissions....................................................................................... 40
3.6RADIO AND SERIAL CONFIGURATION .................................................................... 40
3.6.1Radio Data Rate....................................................................................................... 40
3.6.2Serial Port Settings .................................................................................................. 40
3.6.3Other Settings.......................................................................................................... 41
3.7ACKNOWLEDGED MODE........................................................................................ 42
3.7.1 Auto-Connect Acknowledged mode ................................................................... 42
3.7.2 Single-Connect Acknowledged mode................................................................. 44
3.8DUAL REDUNDANT STANDBY................................................................................ 45
3.9LOW POWER MODE ............................................................................................... 47
3.10OPTIMUM PATH ROUTING...................................................................................... 47
Path Configuration............................................................................................................... 48
Configuring for Modbus Protocol (RTU or ASCII)............................................................ 48
Modbus RTU Protocol......................................................................................................... 48
Modbus ASCII protocol ...................................................................................................... 48
DF1 protocol........................................................................................................................ 48
DNP3................................................................................................................................... 49
3.11ADVANCED SETTINGS -SREGISTERS................................................................... 49
3.12HAYES AT COMMANDS ......................................................................................... 49
3.13AT CONFIGURATION EXAMPLES............................................................................ 50
3.14SWITCH CONFIGURATION ...................................................................................... 52
CHAPTER FOURTROUBLESHOOTING .................................................................... 53
4.1POWER-UP AND NORMAL OPERATION ................................................................... 53
4.2LED INDICATION DIAGNOSTICS CHART................................................................. 54
4.3OPERATING PROBLEMS.......................................................................................... 55
4.4TEST FUNCTIONS ................................................................................................... 56
4.4.1Bit Error Ratio Test (BER)...................................................................................... 56
4.4.2Other Radio Testing - AT&Tx................................................................................ 57
4.4.3On-line diagnostics.................................................................................................. 58
4.5RADIO PATH TESTING............................................................................................ 60
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Page 6 Jul 2010
4.6CHANGING THE RADIO PARAMETERS .................................................................... 61
4.7DIAGNOSTIC MESSAGES ........................................................................................ 62
4.8DUAL REDUNDANCY ............................................................................................. 63
4.8.1Firmware versions prior to 3.03 .............................................................................. 66
CHAPTER FIVESPECIFICATIONS ............................................................................. 68
APPENDIX A HAYES COMMANDS............................................................................. 70
APPENDIX B RESPONSE CODES ................................................................................ 79
APPENDIX C S-REGISTERS.......................................................................................... 80
User Manual
INM WMO400S_v3 03_2.doc Page 7
Chapter One INTRODUCTION
1.1 General
The WMO-400S radio modem provides reliable radio modem operation with advanced
communication control and diagnostics functions. Radio modems transmit serial data over a
long distance via radio. The serial data is not changed - the output data is the same as the
input data. Although the WMO-400S is intended to be simple in its application, it also
provides many sophisticated features. This manual should be read carefully to ensure that the
modules are configured and installed to give reliable performance.
Each WMO-400S module will connect to a host device by RS232 or RS485 serial connection.
Examples of host devices are PLC’s, data loggers, intelligent transducers and computers. The
WMO-400S unit can receive data from the host device and transmit this data by radio to
another (or several) WMO-400S module. The other module will recreate the serial data and
output it as either a RS232 or RS485 serial signal. The WMO-400S unit provides two-way
communications - each module can accept serial data and also output serial data.
The WMO-400S module has two data ports (one RS232 and one RS485) and can connect to
two host devices independently. The WMO-400S also has another RS232 port (via a RJ45
connector) which can be used only for configuration or access to diagnostics information - the
RS232 data port can also be used for configuration and diagnostics.
RS232 is an electrical standard format for a full duplex point-to-point serial connection.
RS485 is an electrical standard format for a half-duplex multidrop serial connection. Up
to 32 devices can communicate on a common RS485 serial bus.
Each WMO-400S can simultaneously
connect to signals from both RS232 and
RS485. In addition, RS232 data from
one host device can be transmitted to a
remote WMO-400S unit and output as
RS485 data to another host device.
The unit includes a fixed frequency
radio transceiver with overall frequency
range 360MHz to 512MHz, in seven
radio bands, each 20MHz wide. The
user can configure the radio frequency
within the 20MHz band (refer to
Diagnostics section).
The WMO-400S is available with a high power radio (0.5 – 5W) suitable for licensed narrow-
width channels (12.5, 20 or 25KHz). The unit is also available with a lower power radio (10 –
500mW) suitable for license-free narrow-width channels, in countries where these are
available.
The operating parameters of the WMO-400S are configured from a PC using a Microsoft
Windows configuration package provided free with the module, or from a PC terminal using
Hayes commands.
WMO-400S Radio Modem Module
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Ordering Information
WMO - Frequency – Power Channel
Frequency 440 440MHz center frequency, configurable between 430MHz and
450MHz
460 440MHz center frequency, configurable between 450MHz and
470MHz
480 480MHz center frequency, configurable between 470MHz and
490MHz
Power L10 – 500mW H0.5 – 5W
Channel N 12.5 KHz W 20/25 KHz
For example if a project required a 458.925MHz frequency, 5W transmit power with wideband
channel, the part number would be WMO-460S-HW
If a specific frequency and power level is specified on the purchase order, then the radio will be
delivered on that frequency and power level for a fee.
1.1.1 Basic Operation
The operation of the WMO-400S radio modem is relatively simple. As data is received at the
serial port, the data is transmitted on the radio channel. Up to 1020 bytes of data can be
transmitted in one transmission. The radio transmission commences when the first data byte
is received, and ends when there are no more data bytes in the input buffer, or when the
number of bytes transmitted equals the maximum message length (user configurable - default
1020 bytes). If more than 1020 bytes is input, the WMO-400S unit will transmit the first 1020
bytes, then the next 1020 bytes, and so on until all of the data has been transmitted.
Because the radio data rate could be less than the input serial data rate, an input memory
buffer of up to 8Kbytes is provided. The RS232 connection provides CTS control to prevent
the buffer overflowing. There are no data flow control signals for RS485.
1.1.2 Operating Modes
A radio channel cannot provide as secure a data channel as a wired connection. The WMO-
400S uses a radio band with a low level of natural or industrial noise, however there is a
chance of interference from other users on the radio channel. We recommend that the flow of
data over the radio channel is controlled by using error detection and “handshaking” - that is,
returning an acknowledgment transmission if a data packet is received on the radio channel
without error. This function can be performed by either the host devices or the WMO-400S
modules.
The modules may be configured by the user to operate in one of two modes. In
Unacknowledged mode, it is assumed that the host devices control the flow of data - the
WMO-400S does not provide handshaking. In Acknowledged mode, the WMO-400S units
provide handshaking to control the flow of data.
The RS485 port always operates in Unacknowledged mode.
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INM WMO400S_v3 03_2.doc Page 9
1.1.3 Repeater Functionality
A WMO-400S unit can act as a repeater for other units. A repeater receives a radio message
from one unit and re-transmits it on to another unit.
Up to seven repeater addresses can be configured in a radio link.
If transmitting to the wildcard 0 address in Unacknowledged mode (that is, a broadcast
transmission), then the repeater unit can be configured to also output the data to its own host
device.
1.1.4 Hot Redundant Standby
Two WMO-400S units can be installed together in a Dual Redundant relationship - an active
unit with a hot redundant standby. One unit is configured as a “primary” unit and the other
the “secondary”. The secondary unit acts as a standby for the primary.
Under normal operation, the primary unit is active and the standby is inactive. If the internal
diagnostics in the primary detects a fault or an operating problem, the primary stops normal
operation and the secondary becomes active. The inactive unit is powered and operational,
however communications out of the unit via the radio transmitter and RS485 port is disabled.
Both units have the same configuration apart from primary/secondary selection.
1.2 Unacknowledged Mode
The default configuration of the WMO-400S modem is unacknowledged mode - the modules
are set in this mode at the factory.
In unacknowledged mode,
units do not provide
handshaking functions to
control the flow of data.
Messages are not
acknowledged, and are sent
on a “Best attempt” basis. It
is up to the host equipment
to determine if data is lost
or corrupted.
To improve reliability in this mode, units may be configured to send each message multiple
times (configured in S-Register S29). The receiving unit will detect repeat messages and only
send the data out the serial port once.
Each modem is configured with a separate unit address. In Unacknowledged mode, messages
may be sent:
WMO-400S Radio Modem Module
Page 10 Jul 2010
to a particular modem
by using the remote
unit’s address, or
to all modems in the
system, as a
broadcast message by
using the wildcard
address 0. The
wildcard address is
used to send a
message to a group of
modems.
Data received at the
serial port is transmitted out of the radio port, addressed to the configured destination WMO-
400S module, or to all modules by using address 0. Data received from the radio with the
correct addressing is transmitted out of one of the serial ports (RS232 or RS485).
Prior to transmitting, units will listen to the radio channel to ensure that it is clear - units will
hold off from transmitting until the radio channel is clear.
At the RS232 port, the CTS pin can be configured to go high while there is space in the input
data buffer - otherwise it is always high.
Host devices should provide a suitable protocol to ensure that error checking, handshaking
and implementation of an appropriate re-transmission scheme is provided. This mode of
operation is particularly suited to devices designed to operate over a multidrop network, such
as PLC systems designed for operation over a RS-485 network.
If error checking is not configured at the receiving unit, data will start to be output
immediately after the first byte of data has been received. If error checking is configured, data
will be output approx 1mSec after the end of the message. For example, a message with 20
bytes of data transmitted at 19200 bits/sec will begin to be output approx 23 msec after the
data is input, if there is no error checking, or 31 msec after the data is input if error checking
is configured - this assumes the minimum lead-in time of 20 msec is configured.
1.3 Acknowledged Mode
In Acknowledged mode,
data is transferred between
the RS-232 ports of two
modules (that is, a point to
point link). One of the
modules is configured as a
“master” (or initiator) unit
and the other as a “slave”
(or responder) unit. There
can be many slave units in
the system, however the
master unit will only link to one slave at any one time.
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Note that Acknowledged mode only applies to the RS-232 port. The RS-485 port always
operates in Unacknowledged mode.
To establish a link, the master unit transmits a special “connect” message. This initial message
does not include any data. If the addressed slave unit receives the connect message, and is not
already connected to another WMO-400S unit, it will return an acknowledgment message.
Both units will activate their DCD LED, and also activate their DCD output signal (if
configured). If the master unit does not receive the acknowledgment, the DCD output will
reset. When the connection is made (DCD set), the WMO-400S units can transmit data to
each other.
A master can be configured to connect to a pre-configured slave address in two ways:
on power up - the master will only connect to one fixed slave address and if the
connection link fails, the master will continuously try to make a new connection, or
it can be “commanded” by its host device using AT commands - the host device can
control the master WMO-400S to “dial” a slave address, connect, transfer data, and then
disconnect (or “hang up”), and connect to a different slave address.
Once the communications channel has been established, the WMO-400S unit will accept input
data and send radio messages with data. When a WMO-400S unit receives a radio message, it
will check the system address and destination address, and also the error-check (optional). If
these are correct, it will return a ACK (acknowledgment) message to the source unit. If the
system address or destination address is not correct, or if the error-check is not correct, then
no return message is sent.
There can also be up to five intermediate repeaters in the link. Each WMO-400S unit is
configured with a unit address - only the unit with an address matching the destination address
of the radio message will process the message and output the serial data.
Establishing a Communications Link
Master Unit Slave Unit
Listen to ensure channel is clear
If clear, transmit “connect” message
Radio TX LED flashes
----------------->
Receives message
Radio RX LED flashes
Check system and destination
address
If OK, set DCD LED and output
Radio RX LED flashes
<-----------------
If message OK, transmit back
an ACK message.
Radio TX LED flashes
Acknowledgment received okay
communication link established
Set DCD LED and output
WMO-400S Radio Modem Module
Page 12 Jul 2010
If the source unit does not receive an ACK message, it will re-transmit the same message. It
will attempt to transmit the message the configured number of times (S-Register S30). If the
unit still does not receive an ACK message after the configured number of attempts, it will
reset the LINK LED, and reset the DCD output on the DB9 RS232 port and reset the DIO
output (if configured).
During normal operation, if there has been no radio activity for a period (called the “link
check” period), the master unit will transmit a “check” message to check the radio path. The
link check period is user-configurable (S-Register S6). If the slave doesn’t receive any
messages within the configured link check timeout (Configuration Setting \T), it will drop the
radio link, and turn off the LINK LED, and reset the DIO and DCD signals (if configured).
Successful Communications
Source Module Destination Module
Serial data is received
Serial LED flashes
Listen to ensure channel is clear
If clear, transmit message
Radio TX LED flashes
----------------->
Receive message
Radio RX LED flashes
Check system and destination
address
If OK, check error-check
Radio RX LED flashes
<-----------------
If message okay, transmit
back an ACK message.
Radio TX LED flashes
Acknowledgment received okay -
communication complete Serial data is output
Serial LED flashes
Unsuccessful Communications
Source Module Destination Module
Listen to ensure channel is clear
If clear, transmit message
TX LED flashes ----------------->
Receives message
RX LED flashes
Check system and destination
address
If incorrect, transmit no message
and no serial output.
No ACK received
Retry multiple times (Configure With
S-Register S30) ----------------->
If no ACK message received after
all attempts
“NO CARRIER” message sent to
host
DCD signal and DCD LED reset
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1.4 Security Encryption
Some applications require that the system be made secure from eavesdropping and hacking.
To provide for these applications, the modem supports AES-128 data encryption.
The modem may be configured to transmit messages with or without encryption, accept
messages without encryption, or to require that received messages are encrypted.
Messages sent with encryption have an additional 16 bytes of data added to the start of the
radio message (the initialization vector).
1.5 Serial and Radio Data
The WMO-400S module provides a full-duplex RS232 serial port and half-duplex RS485
serial port. The radio communications is half-duplex. Many applications use full duplex
RS232 communications but do not require full duplex - the protocol used operates at half-
duplex and will operate with the WMO-400S without problems. If an application really
requires full duplex communications, then the WMO-400S should not be used.
Data input at the serial port is placed into the input buffer. This buffer will store up to
8Kbytes of data, and CTS/RTS control can be configured on the RS232 port to prevent
overflow.
When the WMO-400S unit detects data in the input buffer, it initiates a radio message. The
radio message will end when the number of transmitted bytes reaches the maximum message
length (configurable by the user), or if the input buffer becomes empty.
If the configured serial data rate is the same or more than the radio data rate, then data is
transmitted as soon as it enters the input buffer - data “streams” from the input buffer to the
radio port. If the serial rate is less than the radio rate, then the transmission will be delayed
for a period to allow sufficient data to build up in the input buffer to avoid the radio emptying
the input buffer before a complete serial message has been input. This delay is configurable
separately for the RS232 and RS485 serial ports. Alternatively a Transmitter Hold up time can
be configured (S-Register S27) to keep the transmitter keyed up between characters.
The radio transmission will stop when the input buffer is empty or when the radio has
transmitted the maximum number of bytes (user configurable - maximum 1020 bytes). If
there is still data in the input buffer, the WMO-400S will start another radio transmission.
An error-check can be added to each radio message - this is a user-configurable selection. If
error checking is configured, then a 16 bit CRC error-check is added to the end of the
transmitted data packet. The receiving module will receive the full data packet and check the
CRC before outputting the data.
The maximum size of the data packet is configurable by the user (maximum is 1020 bytes). If
less data than the maximum size is input to the WMO-400S, then the WMO-400S will
transmit the actual data input. If more data is input than the maximum size, then the WMO-
400S will transmit multiple packets until all of the data is transmitted.
Because of radio start-up delays, the effective radio data rate will be lower than the
transmitted data rate. If you are sending large blocks of data, and the serial rate is equal or
WMO-400S Radio Modem Module
Page 14 Jul 2010
more than the radio rate, we recommend that you use CTS/RTS flow control to prevent the
input buffer from overflowing.
1.5.1 PLC-Mode
The WMO-400S will operate most efficiently when the serial data rate is higher or the same
as the radio data rate. If the serial data rate is less than the radio rate, there is a risk that the
radio will empty the input buffer too quickly, resulting in a single input message being broken
into more than one output messages. Many host protocols such as those used by PLC’s, will
not accept a message being broken into sections with delays between the sub-sections.
To avoid this occurring, the WMO-400S will automatically delay the radio transmission
starting if the serial rate is less than the radio rate. This is called “PLC Mode”. The radio will
not start transmitting until a certain number of bytes have been input into the input buffer.
The WMO-400S calculates the number of starting bytes depending on the values of the
configured serial and radio rates. The number of bytes to start transmitting is stored in register
S18 (S20 for RS485)) - when a configuration is entered whereby the serial rate is less than the
radio rate, the WMO-400S configuration software will automatically enter an appropriate
value in S18. The user can change this value. If the serial rate is the same as the radio rate,
or more, than there is no delay.
There is an automatic protection - if a certain time has elapsed and the number of starting
bytes has not been input, then the radio will start transmitting. This is an override protection.
The WMO-400S will automatically calculate the override time based on the configured serial
rate and S18 (the number of bytes required to start). The override time is stored in register
S19 (S21 for RS485) - this value can also be changed by the user.
In applications where the extra delay introduced by buffering data at the sending modem is
unacceptable, an alternative is to configure a “Transmitter Hold up” time (S-Register S27).
This keeps the transmission keyed up between data characters.
1.5.2 Character Type
The WMO-400S may be configured by the user to
recognize the following types of characters - 7 or 8
data bits, even or odd or no parity, 1 or 2 stop bits.
Most applications will require the character type to be
the same at each WMO-400S modem in the system.
Nevertheless, the character type may be configured to
be different at different WMO-400S modems. Data is
transmitted by radio as an eight-bit byte without stop
or start bits. If the input data is 7 data bits, then the
byte transmitted by radio comprises the 7 bits plus a zero bit. Input characters with 8 bits are
transmitted as just the 8 data bits, with no parity. Because the data is transmitted without
parity, the user may configure CRC error checking to be added to each transmitted data
packet. Data is output at the destination module based on the character type configured at that
module - that is, the start/stop bits and parity is added to the radio data.
Data Parity Stop
7 Even 1
2
Odd 1
2
None 2
8 Even 1
Odd 1
None 1
2
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1.5.3 Serial Data Rate
The communications baud rates supported on both the RS232 serial port and the RS485 serial
port are 600, 1200, 2400, 4800, 9600, 14400, 19200, 28800, 31250, 38400, 57600, 76800, 93750,
115200 and 187500 baud - the user selects one of these rates during the configuration of the
modem.
The RS232 and RS485 ports may be configured with separate data rates.
1.5.4 Radio Data Rate
The data is transmitted by radio as direct modulated synchronous data at 1200, 2400, 4800
9600, or 19200 bits/second - (19200 baud only operates with 25KHz channel widths). The
user must configure the radio data rate at each WMO-400S module. The configured radio
data rates must be the same for each module in a system.
The WMO-400S uses four-level frequency modulation for the highest data rates - 9600 b/s
for 12.5KHz channels and 19200 b/s for 25KHz channels. The other rates use two level
frequency modulation. Two level modulation results in less data errors, resulting in more
reliable operation. It is recommended that radio rates of 4800 (12.5KHz) or 9600 (25KHz) be
used unless the application requires the higher data rates.
1.5.5 Radio Message
The radio message includes the following :-
A 40 msec leading sequence of alternating 1’s and 0’s provides the receiving unit with
time to capture and lock onto the incoming signal (the lead-in time can be configured to
be longer for systems using talk-through repeaters).
A system address is superimposed on each message to provide discrimination between
different WMO-400S systems on the same radio channel. Each WMO-400S unit in the
same system must be configured with the same system address - refer Configuration
section. Although other WMO-400S modules may hear the radio transmissions, because
they have a different system address, the radio transmission is ignored and no serial data
is output.
Addressing for the sending unit, any repeater units, and the final destination unit indicates
where the message is to be sent and how to get there.
An error-check (16 bit CRC) and security encryption (AES128) may be configured by the
user.
Up to 1020 bytes of data may be transmitted in a message - the maximum message size is
configurable between 1 and 1020 bytes. The data consists of a sequence of 8 bit bytes. Start,
stop and parity bits are not transmitted, but they are re-generated at the receiving unit (if
configured).
WMO-400S Radio Modem Module
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The time taken to transmit a message is :-
Section Item Number Time (At 9600 Baud)
PEAMBLE Lead-in 40 msec Default
(Configurable) 40 msec
HEADER System Address 2 Bytes 2.08 msec
Header Control 2 Bytes 2.08 msec
Source Address 1 Byte 1.04 msec
Destination Address 1 Byte 1.04 msec
Intermediate Address 1 Byte per address 1.04 msec for each address
Header Error Check 1 Byte 1.04 msec
ENCRYPTION Initialisation Vector 16 Bytes (if enabled) 16.64 msec (If configured)
DATA Message Data Data Bytes 1.04 msec x no of data bytes
CHECK CRC Error Check 2 bytes (if enabled) 2.08 msec (If CRC
configured).
The time for each byte is 1.04msec @9600 bits/sec, 2.08 msec at 4800 bits/sec, and 4.16 msec
at 2400 bits/sec.. If error checking is not configured at the receiving unit, data will start to be
output immediately after the first data byte has been received. If error checking is configured,
data will be output approx 1msec after the end of the message. For example, a message with
20 bytes of data transmitted at 9600 bits/sec with no repeaters, will start to be output approx
71msec after the data is input, if error checking is configured, and will start to be output
approx 47 msec after the data is input if no error checking is configured.
A “transmit delay” time and a “receive delay” time may also be configured. These parameters
may be used to fine tune and give priority to different WMO-400S units in a system.
After each message is transmitted, a WMO-400S unit will not transmit another message
during the transmit delay time. This could be used to allow a reply message to be received
before the next message is sent.
After a message is received, a message will not be transmitted during the receive delay time.
This could be used to delay a reply message until other messages have been sent.
1.6 Addressing
A WMO-400S network comprises modules with the same "system" address. Only modules
with the same system address will communicate with each other. This feature allows more
than one system to operate in the same area on the same radio channel.
A WMO-400S must also be configured with a “unit” address - this gives the module a unique
identification. The unit address is used to identify the two data ports on each WMO-400S.
The RS232 port is accessed by addressing the configured unit address. The RS485 port is
accessed by addressing the configured unit address +128. So, to access the RS232 port on unit
7, use address 7. To access the RS485 port on this unit, use address 135 (128+7).
Addresses 0 and 128 are reserved as “wildcard” addresses. Sending a message to address 0
results in all modules accepting the message. Address 0 refers to every RS232 port in the
system. Address 128 is the wildcard address for every RS485 port in the system.
User Manual
INM WMO400S_v3 03_2.doc Page 17
1.6.1 Multiple Device Connectivity (MDC)
Because each serial port is individually
addressed, the WMO-400S is able to
connect to two serial devices and
manage two independent wireless links.
This is called Multiple Device
Connectivity, or MDC functionality.
Some of the features if MDC are:
Each serial port is configured
individually however with the same
system address.
The device connected to the RS485
port can link to the RS485 port or the RS232 port on another WMO-400S - the same
applies to the RS232 device. However if a wild-card address is used (0 or 128), then all
remote serial ports must be the same - that is, all R485 or all RS232.
The RS485 port always operates in Unacknowledged mode. The RS232 port can be in
Unacknowledged or Acknowledged mode. The DCD status indication will relate to the
RS232 port.
Each wireless link can include repeater addresses.
Because both communications channels use the same radio channel, activity on one port
may impact communications on the other port, by introducing delays in message
transmission.
1.7 Optimum Path Routing
Optimum Path Routing (OPR) is an advanced feature providing fast and efficient radio
networking. OPR is a protocol-specific feature using the link layer of a variety of host
protocols, allowing routing of messages for up to 64 different host addresses.
Supported host protocols are:
DF1 (half duplex master and slave),
Modbus (Master and Slave) - RTU and ASCII formats,
Profibus (Peer-to-Peer) and
DNP3 (peer-to-peer).
Under OPR, a “path” is configured for each host protocol address, comprising the WMO-
400S destination address and any WMO-400S repeater addresses in the path. When the
WMO-400S unit receives a data message from its host, the WMO-400S will interrogate the
message for the host destination address and use the pre-configured OPR path to send the
radio message.
For more information, refer to section 3 of this Manual.
WMO-400S Radio Modem Module
Page 18 Jul 2010
1.8 Duty Cycle Limiting
Some licenses require that the modem limits its communications so that it is transmitting for
no more than a maximum proportion of the available time. This applies to European 500mW
unlicensed bands, where the modem must limit its duty cycle to 10%.
Duty cycle limit is set to 100% except for modems which are configured for the European
limited duty cycle bands.
To change the duty cycle limit, use the AT#D command. (AT#D100 for 100%).
Duty cycle limiting must be calculated over a time no greater than one hour. You might prefer
to calculate the duty cycle limit over a shorter time. The AT#T command sets the time in
minutes to use to calculate the duty cycle.
1.9 What Operating Mode to Use ?
1.9.1 Unacknowledged or Acknowledged mode?
Unacknowledged mode provides simpler operation as the units do not acknowledge
transmissions received. However confirmed operation in unacknowledged mode will only occur
if the host devices check the messages and return acknowledgments. Generally, if a device is able
to operate on a RS485 multi-drop serial link, it is suitable for unacknowledged mode.
The RS-485 port only operates in Unacknowledged mode. It is possible for the RS-485 port to be
operating at the same time as the RS-232 port is sending data to another location, using either
Acknowledged or Unacknowledged mode (MDC).
RS-232 links can also be made in Unacknowledged mode - the WMO-400S units can effectively
provide a “multi-drop” network for RS232 devices, provided the devices use a communications
protocol that includes addressing and message acknowledgments.
Normally Unacknowledged mode would be used with PLC’s and similar devices.
Acknowledged mode is suitable for point-to-point RS-232 links where the host devices do not
provide addressing or message acknowledgment. Multi-point networks are possible in
Acknowledged mode, however a “master” host device must control connecting and disconnecting
to remote units using AT commands.
It is possible to configure different units in the same system with different operating modes,
however this requires care. A WMO-400S unit configured in one mode can act as a repeater for
messages sent between two WMO-400S units configured in the other mode, and it is always
possible to send Unacknowledged mode messages to the RS-485 port on a module regardless of
the configuration of the RS-232 port.
User Manual
INM WMO400S_v3 03_2.doc Page 19
1.9.2 Error Check
Error-checking may be configured in both Unacknowledged and Acknowledged mode. When the
error-check is configured, a 16-bit CRC (Cyclic Redundancy Check) attached to the end of each
message. This check is used to detect any corruption of the data when it is received at another
WMO-400S unit.
Error checking is individually selected for the RS232 port and the RS485 port.
When a unit receives a radio message with error-check, it will not output data until it has received
the whole message and ensured that the error-check is correct. If the unit does not have error-
check configured, then it will output data as it is received, streaming from the radio out the serial
port. Hence operation of the units is faster if error-check is not configured.
Usually units in the same system will have the same error-check configuration, however it is
possible for users to configure the units differently. Each message sent indicates within the
message header whether it uses error-checking or not., so a single modem can receive messages
with and without error checking without requiring changes to the configuration.
Error-check is strongly recommended for Acknowledged mode operation. If error-check is not
configured, then a WMO-400S unit will transmit an acknowledgment message (ACK) whenever
it receives a radio message, without checking for errors. If error-check is configured, the unit
will only transmit an ACK message if the error-check is correct.
When using OPR with Modbus RTU or DNP3 protocols, error check should be disabled as these
incorporate their own error check within the data frame.
When using OPR with Modbus ASCII protocol, error check should be enabled as this protocol
only incorporates a weak LRC error check.
When using OPR with DF1 protocol, Error check must be enabled if the DF1 protocol is
configured for Block Character Check (BCC). Error check must be disabled if the DF1 protocol
is configured for Cyclic Redundancy Check (CRC). Best performance is found when DF1 is
configured to use CRC, and Error check is disabled on the WMO-400S.
WMO-400S Radio Modem Module
Page 20 Jul 2010
Chapter Two INSTALLATION
2.1 General
The WMO-400S module is housed in a rugged aluminium case suitable for DIN-rail
mounting. Terminals will accept wires up to 2.5 sqmm (12 gauge) in size.
Normal 110-240V AC supply should not be connected to any terminal of the WMO-400S
module. Refer to Section 2.3 Power Supply.
To operate this equipment legally the user must operate on a designated license-free radio
channel and within the operating parameters of the license-free channel, or obtain a radio
operating license from the responsible government agency. This is done so the government
can coordinate radio users in order to minimize interference.
Before installing a new system, it is preferable to bench test the complete system.
Configuration problems are easier to recognize when the system units are adjacent. Following
installation, the most common problem is poor communications caused by incorrectly
installed antennas, or radio interference on the same channel, or the radio path being
inadequate. If the radio path is a problem (ie path too long, or obstructions in the way) then
higher performance antennas or a higher mounting point for the antenna may rectify the
problem. Alternately, use an intermediate WMO-400S Module as a repeater.
The foldout sheet WMO-400S Installation Guide provides an installation drawing
appropriate to most applications. Further information is detailed below.
Each WMO-400S module should be effectively earthed via the "GND" terminal on the WMO-
400S module - this is to ensure that the surge protection circuits inside the WMO-400S
module are effective.
2.2 Antenna Installation
The WMO-400S module will operate reliably over large distances. The distance which may
be reliably achieved will vary with each application - depending on the type and location of
antennas, the degree of radio interference, and obstructions (such as hills or trees) to the radio
path. The expected range for radio data rates of 4800 bits/sec is up to 60km (40 miles),
depending on installation, site and path terrain. The expected range at 19200 bits/sec (with
25KHz bandwidth) or 9600 bit/sec (with 12.5KHz), is up to 30 km (20 miles) line-of-sight.
Where it is not possible to achieve reliable communications between two WMO-400S
modules, then a third WMO-400S module may be used to receive the message and re-transmit
it. This module is referred to as a repeater.
An antenna must be connected to each WMO-400S module using the female SMA connector
at the top of the module.
To achieve the maximum transmission distance, the antennas should be raised above
intermediate obstructions such that the radio path is true “line of sight”. Because of the
curvature of the earth, the antennas will need to be elevated at least 5 metres (15 feet) above
ground for paths of 5 km (3 miles). For short distances, the modules will operate reliably with
some obstruction of the radio path. Obstructions which are close to either antenna will have
more of a blocking effect than obstructions in the middle of the radio path. For example, a
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