Murata WIT910 Quick setup guide

©2010-2015 by Murata Electronics N.A., Inc.
WIT910 Integration guide (R) 05/14/15
www.murata.com
WIT910 900 MHz
Spread Spectrum
Wireless Industrial
Transceiver
Integration *XLGH

Important Regulatory Information
Cirronet Product FCC ID: HSW-910M
IC 4492A-910M
Note: This unit has been tested and found to comply with the limits for a Class A digital device,
pursuant to part 15 of the FCC Rules. These limits are designed to provide reasonable protection
against harmful interference when the equipment is operated in a commercial environment. This
equipment generates, uses, and can radiate radio frequency energy and, if not installed and used
in accordance with the instruction manual, may cause harmful interference to radio
communications. Operation of this equipment in a residential area is likely to cause harmful
interference in which case the user will be required to correct the interference at their expense.
FCC s MPE Requirements
Information to user/installer regarding FCC s Maximum Permissible Exposure (MPE) limits.
Notice to users/installers using the 8.5 dBi Yagi antenna with the WIT910.
FCC rules limit the use of this antenna, when connected to the WIT910 module, to point-to-point
applications only. It is the responsibility of the installer to ensure that the system is prohibited
from being used in point-to-multipoint applications, omni-directional applications, and
applications where there are multiple co-located intentional radiators transmitting the same
information. Any other mode of operation using this antenna is forbidden.
Notice to WIT910 users/installers using the following fixed antennas:
Cushcraft 8.5 dBi Yagi
The field strength radiated by this antenna, when connected to a transmitting WIT910, may
exceed FCC mandated RF exposure limits. FCC rules require professional installation of these
antennas in such a way that the general public will not be closer than 23 cm from the radiating
aperture of this antenna. End users of these systems must also be informed that RF exposure
limits may be exceeded if personnel come closer than 23 cm to the aperture of this antenna.
Notice to WIT910 users/installers using the following fixed antennas:
Cushcraft 6 dBi Monopole Cushcraft 3 dBi Omni Ace 2dBi dipole
The field strength radiated by any one of these antennas, when connected to a transmitting
WIT910, may not exceed FCC mandated RF exposure limits. FCC rules require professional
installation of these antennas in such a way that the general public will not be closer than 20 cm
from the radiating aperture of any of these antennas. End users of these systems must also be
informed that RF exposure limits may be exceeded if personnel come closer than 20 cm to the
apertures of any of these antennas.
Changes or modifications not expressly approved by the party responsible may void the users ability to
operate the equipment.
©2010-2015 by Murata Electronics N.A., Inc.
WIT910 Integration guide (R) 05/14/15
www.murata.com

TABLE OF CONTENTS
1. INTRODUCTION ......................................................................................................................1
1.1 Why Spread Spectrum? ........................................................................................................1
1.2 Frequency Hopping vs. Direct Sequence..............................................................................2
2. RADIO OPERATION................................................................................................................4
2.1 Synchronization and Registration.........................................................................................4
2.2 Data Transmission ................................................................................................................5
2.2.1. Point-to-Point.............................................................................................................5
2.2.2. Point-to-Multipoint ....................................................................................................6
2.2.3. Handle Assignment....................................................................................................6
2.2.4. TDMA Operation........................................................................................................7
2.2.5. Full Duplex Communication......................................................................................9
2.2.6. Error-free Packet Transmission Using ARQ..............................................................9
2.3 Modes of Operation............................................................................................................10
2.3.1. Control and Data Modes ..........................................................................................10
2.3.2. Sleep Mode ..............................................................................................................10
2.3.3. Low Power Mode and Duty Cycling .......................................................................11
2.3.4. RF Flow Control Mode.............................................................................................11
3. PROTOCOL MODES ..............................................................................................................12
3.1.1. Data Packet ..............................................................................................................14
3.1.3. Connect Packet.........................................................................................................15
3.1.4. Disconnect Packet (base only, receive only) ..........................................................15
4. MODEM INTERFACE............................................................................................................16
4.1 Interfacing to 5-Volt Systems.............................................................................................17
4.2 Evaluation Unit and OEM Module Differences .................................................................17
4.3 Three Wire Operation.........................................................................................................17
4.4 Power-On Reset Requirements...........................................................................................18
4.6 Received Signal Strength Indicator ....................................................................................19
5. MODEM COMMANDS...........................................................................................................20
5.1 Serial Commands................................................................................................................20
5.2 Network Commands...........................................................................................................22
5.3 Protocol Commands............................................................................................................24
5.4 Status Commands ...............................................................................................................27
5.5 Memory Commands ...........................................................................................................28
5.6 Modem Command Summary..............................................................................................29
6. WIT910 DEVELOPER’S KIT .................................................................................................30
7. WinCOM...................................................................................................................................31
Starting the program ..................................................................................................................33
Function Keys............................................................................................................................36
WinCom Tools...........................................................................................................................37
©2010-2015 by Murata Electronics N.A., Inc.
WIT910 Integration guide (R) 05/14/15
www.murata.com

Script Commands.......................................................................................................................39
Demonstration Procedure ..........................................................................................................41
7.6 Troubleshooting..................................................................................................................42
8. APPENDICES ..........................................................................................................................44
8.1 Technical Specifications.....................................................................................................44
8.1.1. Ordering Information...............................................................................................44
8.1.2. Power Specifications................................................................................................44
8.1.3. RF Specifications.....................................................................................................44
8.1.4. Mechanical Specifications .......................................................................................44
8.2 Serial Connector Pinouts ....................................................................................................45
8.3 Approved Antennas ............................................................................................................45
8.4 Technical Support...............................................................................................................46
8.5 Reference Design................................................................................................................47
8.6 Mechanical Drawing – WIT910 .........................................................................................48
8.7 Warranty .............................................................................................................................49
©2010-2015 by Murata Electronics N.A., Inc.
WIT910 Integration guide (R) 05/14/15
www.murata.com

WIT910
1. INTRODUCTION
The WIT910 radio transceiver provides reliable wireless connectivity for either
point-to-point or multipoint applications. Frequency hopping spread spectrum
technology ensures maximum resistance to noise and multipath fading and robustness in
the presence of interfering signals, while operation in the 900MHz ISM band allows
license-free use and worldwide compliance. Standard communication rates between the
WIT910 and the host are supported between 2400bps and 115bps. Non-standard rates
are supported as well. An on-board buffer and an error-correcting over-the-air protocol
provide smooth data flow and simplify the task of integration with existing applications.
-Multipath fading impervious
frequency hopping technology
with 54 frequency channels
(902 to 927 MHz).
- Supports point-to-point or
multipoint applications.
- Meets FCC rules 15.247 for
license-free operation.
- 20+ mile range with omni
antenna.
- Transparent ARQ protocol
w/512byte buffer ensures data
integrity.
- Digital addressing supports up to
64 networks, with 62 remotes per
network.
- Low power 3.3v CMOS signals
- Selectable 10mW, 100mW or
500mW transmit power.
- Built-in data scrambling reduces
possibility of eavesdropping.
- Nonvolatile memory stores
configuration when powered off.
- Smart power management features
for low current consumption.
- Dynamic TDMA slot assignment
that maximizes throughput.
- Simple serial interface handles both
data and control at up to 115.2 bps.
1.1 Why Spread Spectrum?
The radio transmission channel is very hostile, corrupted by noise, path loss and
interfering transmissions from other radios. Even in a pure interference-free
environment, radio performance faces serious degradation through a phenomenon
known as multipath fading. Multipath fading results when two or more reflected
rays of the transmitted signal arrive at the receiving antenna with opposing phase,
thereby partially or completely canceling the desired signal. This is a problem
particularly prevalent in indoor installations. In the frequency domain, a multipath
fade can be described as a frequency-selective notch that shifts in location and
intensity over time as reflections change due to motion of the radio or objects within
its range. At any given time, multipath fades will typically occupy 1% - 2% of the
band. This means that from a probabilistic viewpoint, a conventional radio system
faces a 1% - 2% chance of signal impairment at any given time due to multipath.
©2010-2015 by Murata Electronics N.A., Inc.
WIT910 Integration guide (R) 05/14/15
1 of 49
www.murata.com

WIT910
2
Spread spectrum reduces the vulnerability of a radio system to interference from
both jammers and multipath fading by distributing the transmitted signal over a
larger region of the frequency band than would otherwise be necessary to send the
information. This allows the signal to be reconstructed even though part of it may be
lost or corrupted in transit.
Figure 1
Narrowband vs. spread spectrum in the presence of interference
1.2 Frequency Hopping vs. Direct Sequence
The two primary approaches to spread spectrum are direct sequence (DS) and
frequency hopping (FH), either of which can generally be adapted to a given
application. Direct sequence spread spectrum is produced by multiplying the
transmitted data stream by a much faster, noise-like repeating pattern. The ratio by
which this modulating pattern exceeds the bit rate of the baseband data is called the
processing gain, and is equal to the amount of rejection the system affords against
narrowband interference from multipath and jammers. Transmitting the data signal
as usual, but varying the carrier frequency rapidly according to a pseudo-random
pattern over a broad range of channels produces a frequency hopping spectrum
system.
©2010-2015 by Murata Electronics N.A., Inc.
WIT910 Integration guide (R) 05/14/15
2 of 49
www.murata.com

WIT910
Figure 2
Forms of spread spectrum
One disadvantage of direct sequence systems is that due to spectrum constraints and
the design difficulties of broadband receivers, they generally employ only a minimal
amount of spreading (typically no more than the minimum required by the regulating
agencies). For this reason, the ability of DS systems to overcome fading and in-band
jammers is relatively weak. By contrast, FH systems are capable of probing the
entire band if necessary to find a channel free of interference. Essentially, this
means that a FH system will degrade gracefully as the channel gets noisier while a
DS system may exhibit uneven coverage or work well until a certain point and then
give out completely.
Because it offers greater immunity to interfering signals, FH is often the preferred
choice for co-located systems. Since direct sequence signals are very wide, they
tend to offer few non-overlapping channels, whereas multiple hoppers may
interleave with less interference. Frequency hopping does carry some disadvantage
in that as the transmitter cycles through the hopping pattern it is nearly certain to
visit a few blocked channels where no data can be sent. If these channels are the
same from trip to trip, they can be memorized and avoided; unfortunately, this is
generally not the case, as it may take several seconds to completely cover the hop
sequence during which time the multipath delay profile may have changed
substantially. To ensure seamless operation throughout these outages, a hopping
radio must be capable of buffering its data until a clear channel can be found. A
second consideration of frequency hopping systems is that they require an initial
acquisition period during which the receiver must lock on to the moving carrier of
the transmitter before any data can be sent, which typically takes several seconds. In
summary, frequency hopping systems generally feature greater coverage and channel
utilization than comparable direct sequence systems. Of course, other
implementation factors such as size, cost, power consumption and ease of
implementation must also be considered before a final radio design choice can be
made.
3
©2010-2015 by Murata Electronics N.A., Inc.
WIT910 Integration guide (R) 05/14/15
3 of 49
www.murata.com

WIT910
2. RADIO OPERATION
2.1 Synchronization and Registration
As discussed above, frequency hopping radios periodically change the frequency at
which they transmit. In order for the other radios in the network to receive the
transmission, they must be listening to the frequency over which the current transmission
is being sent. To do this, all the radios in the net must be synchronized and must be set to
the same hopping pattern.
In point-to-point or point-to-multipoint arrangements, one radio module is designated as
the base station. All other radios are designated remotes. One of the responsibilities of
the base station is to transmit a synchronization signal to the remotes to allow them to
synchronize with the base station. Since the remotes know the hopping pattern, once they
are synchronized with the base station, they know which frequency to hop to and when.
Every time the base station hops to a different frequency, it immediately transmits a
synchronizing signal.
When a remote is powered on, it rapidly scans the frequency band for the synchronizing
signal. Since the base station is transmitting over 54 frequencies and the remote is
scanning 54 frequencies, it can take several seconds for a remote to synch up with the
base station.
Once a remote has synchronized with the base station, it must request registration from
the base station. The registration process identifies to the base station the remotes from
which transmissions will be received and not discarded. Registration also allows tracking
of remotes entering and leaving the network. The base station builds a table of serial
numbers of registered remotes. To improve efficiency, the 24-bit remote serial number is
assigned a 6-bit “handle” number. Two of these are reserved for system use, thus each
base station can register 62 separate remotes. This handle is how user applications will
know the remotes. Note that if a remote leaves the coverage area and then re-enters, it
may be assigned a different handle.
To detect if a remote has gone offline or out of range, the registration must be “renewed”
once every 256 hops. Registration is completely automatic and requires no user
application intervention. When the remote is registered, it will receive several network
parameters from the base. This allows the base to automatically update these network
parameters in the remotes over the air. Once a parameter has been changed in the base, it
is automatically changed in the remotes. The parameters automatically changed are hop
duration and the duty cycle.
At the beginning of each hop, the base station transmits a synchronizing signal. After the
synchronizing signal has been sent, the base will transmit any data in its buffer unless
data transmit delay has been set. The data transmit delay parameter allows for the
transmission of groups of continuous data in transparent mode (protocol mode 00H). The
amount of data that the base station can transmit per hop is determined by the base slot
©2010-2015 by Murata Electronics N.A., Inc.
WIT910 Integration guide (R) 05/14/15
4 of 49
www.murata.com

WIT910
size parameter. The maximum amount of data sent by a base station per hop is 208 bytes.
If there is no data to be sent, the base station will not transmit until the next frequency.
The operation for remotes is similar to the base station without the synchronizing signal.
The amount of data a remote can send on one hop is dependent upon the hop duration,
the base slot size and the number of registered remotes. 212 bytes per hop is the
maximum data length a remote can transmit per hop, subject to limitations imposed by
the hop duration, the base slot size and the number of registered remotes. A detailed
explanation of this relationship is provided in Section 2.2.3. Minimum data length and
data transmit delay operate the same as with the base station.
Except for the registration process which occurs only when a remote logs onto the
network, the whole procedure is repeated on every frequency hop. Refer to the section
on Modem Commands for complete details on parameters affecting the transmission of
data.
2.2 Data Transmission
The WIT910 supports two network configurations: point-to-point and point-to-
multipoint. In a point-to-point network, one radio is set up as the base station and the
other radio is set up as a remote. In a point-to-multipoint network, a star topology is used
with the radio set up as a base station acting as the central communications point and all
other radios in the network set up as remotes. In this configuration, all communications
take place between the base station and any one of the remotes. Remotes cannot
communicate directly with each other. It should be noted that point-to-point mode is a
subset of point-to-multipoint mode and therefore there is no need to specify one mode or
the other.
2.2.1. Point-to-Point
In point-to-point mode, unless data transmit delay or minimum data length have been set,
the base station will transmit whatever data is in its buffer limited to 188 bytes or as
limited by the base slot size. If the base station has more data than can be sent on one
hop, the remaining data will be sent on subsequent hops. In addition to the data, the base
station adds some information to the transmission over the RF link. It adds the address of
the remote to which it is transmitting, even though in a point-to-point mode there is only
one remote. It also adds a sequence number to identify the transmission to the remote.
This is needed in the case of acknowledging successful transmissions and retransmitting
unsuccessful transmissions. Also added is a 24-bit CRC to allow the base to check the
received transmission for errors. When the remote receives the transmission, it will
acknowledge the transmission if it was received without errors. If no acknowledgment is
received, the base station will retransmit the same data on the next frequency hop.
In point-to-point mode, a remote will transmit whatever data is in its buffer up to the limit
of its maximum data length. If desired, minimum data length and data transmit delay can
©2010-2015 by Murata Electronics N.A., Inc.
WIT910 Integration guide (R) 05/14/15
5 of 49
www.murata.com

WIT910
also be set, which force the remote to wait until a certain amount of data is available or
the specified delay is exceeded before transmitting. If the remote has more data than can
be sent on one hop, it will send as much data as possible as a packet, adding its own
address, a packet sequence number and 24-bit CRC. These additional bytes are
transparent to the user application if the protocol mode is 00H (which is the default). In
the event a remote has more data to send, the data will be sent on subsequent hops. If the
transmission is received by the base station without errors, the base station will
acknowledge the transmission. If the remote does not receive an acknowledgment, it will
retransmit the data on the next frequency hop. To the user application, acknowledgments
and retransmissions all take place behind the scenes without the need for user
intervention.
The WIT910 has a point-to-point direct mode which fixes the remote radio’s handle at
30H. This mode is recommended for point-to-point applications, especially if the remote
is likely to periodically leave and re-enter the coverage area of the base. See the section
on Network Commands for details of this mode.
2.2.2. Point-to-Multipoint
In point-to-multipoint mode, data sent from the user application to the base station must
be packetized by the user application unless the remote device can distinguish between
transmissions intended for it and transmissions intended for other remote devices. This is
necessary to identify the remote to which the base station should send data. When the
user packet is received by the remote, if the remote is in transparent mode (protocol mode
0), the packetization bytes are stripped by the remote. In this instance the remote host
receives just data. If the remote is not in transparent mode, the remote host will receive
the appropriate packet header as specified by the remote’s protocol mode. Refer to the
section Protocol Modes for details on the various packet formats.
When a remote sends data to a base station in point-to-multipoint mode, the remote host
does not need to perform any packetization of the data. Remotes can operate in
transparent mode even though the base is operating in a packet mode. The remote will
add address, sequence and CRC bytes as in the point-to-point mode. When the base
station receives the data, the base station will add packetization header bytes according to
its protocol mode setting.
2.2.3. Handle Assignment
Handles are used to reduce overhead by not sending the unique 24-bit serial number ID
of a remote when sending or receiving data. The use of the various protocol modes causes
the base radio to issue CONNECT packets when a new remote registers with the base. In
addition to indicating the presence of a new remote, the CONNECT packets provide the
current relationship between remote serial numbers and handles.
©2010-2015 by Murata Electronics N.A., Inc.
WIT910 Integration guide (R) 05/14/15
6 of 49
www.murata.com

WIT910
When a remote links to a base and requests registration, it requests by default that it be
assigned handle 30H. This default request can be changed by the Set Default Handle
command. If that handle is not currently in use by another remote, the base will assign
that handle to the remote. If the requested handle is already in use by another remote, the
base will assign the next higher handle that is available. Thus, if remote requests handle
30H and that handle is already assigned, the base will assign the remote handle 31H if that
is available. If 31H is already assigned, the base will assign handle 32H is that is available
and so on.
When a remote leaves the coverage area of the base or otherwise loses link, e.g. the
remote was turned off or put into sleep mode, the base detects this event when the remote
does not renew its registration within 255 hops. With the default setting of 25msec per
hop, this could be as along as 6.38 seconds. If within this time the remote re-establishes
link with the base, the previous handle assigned to this remote will still be marked active
in the base radio. Thus the remote will be assigned a new handle. If the base radio is in
one of the protocol modes, a new CONNECT packet will be issued indicating the current
handle assigned to the remote. The remote is identified by the serial number that is
contained in the CONNECT packet.
If the radio is to be used in a point-to-point mode where there is only one base and one
remote, using the point-to-point mode command of the radios will override this handle
mechanism and always assign the remote the same handle.
2.2.4. TDMA Operation
For applications needing guaranteed bandwidth availability, the TDMA operation of the
WIT910 can meet this requirement. In the WIT910 TDMA scheme, each remote has an
assigned time slot during which it can transmit. The base station time slot is set
independently of the remote time slots through the Set Base Slot Size command. The
base station assigns each remote a time slot and informs the remotes of the size of the
time slot. All remote time slots are the same size that is determined by the number of
remotes registered with the base station. The slot size is a dynamic variable that changes
as the number of registered remotes changes. The remotes are continually updated with
the time slot size. This approach continually maximizes the data throughput. The base
station divides the amount of time available per hop by the number of registered remotes
up to a maximum of 16 times slots per hop. If the number of registered remotes is greater
than 16, the time slots will be spread across the required number of hops. For networks
with more than 16 possible remotes, the Set Duty Cycle command must be used to specify
a duty cycle -- the number of hops over which the time slots must be spread. For 1 to 16
remotes, no duty cycle is required; for 17 to 32 remotes a duty cycle of at least ½ is
required; and for 33 to 62 remotes a duty cycle of ¼ or more is necessary. An added
benefit of using the power save mode to set a duty cycle is improved average current
consumption efficiency. Refer to the Status Commands section for details of this
command.
©2010-2015 by Murata Electronics N.A., Inc.
WIT910 Integration guide (R) 05/14/15
7 of 49
www.murata.com

WIT910
When setting up a network, keep in mind that time slot length, maximum packet size and
hop duration are all interrelated. The hop duration parameter will determine the time slot
size and the maximum amount of data that can be transmitted per hop by the remotes.
There is a hard limit of the absolute maximum amount of data that can be sent on any
given hop of 212 bytes regardless of any parameters. (Note that this is different than the
208 byte maximum for the base station.) The base station requires 7.04 ms overhead for
tuning, the synchronization signal and parameter updating, as well as 1.11 ms overhead
for each remote. Thus the amount of time allocated per remote slot is roughly:
hop duration – base slot – 7.04ms - ( # of registered remotes)·1.11ms
( # of registered remotes)
Take for example a network comprised of a base station and 5 remotes. A hop duration
of 25 ms is chosen. We decide that the base station needs to be able to send up to 32
bytes each hop (equivalent to a capacity for the base of 19.2 kbps asynchronous).
Counting the 7.04 ms overhead for the base packet and making use of the fact that our RF
rate is 172.8 kbps, we determine that the base slot requires approximately:
32·8
172.8kbps
+ 7.04 ms = 8.52 ms
Each remote time slot will be:
25 ms – 8.52 ms – (5)·1.11 ms
= 2.18 ms
5
From our RF data rate of 172.8kbps we see that it takes 46.3 µs to send a byte of data, so
each remote will be able to send up to
= 47 bytes of data per hop.
2.18 ms
4
6.3
µ
s
us
However, the WIT910 sends data in groups of 4 bytes. Thus, each remote will be able to
send 44 bytes of data. Note that the 44 bytes is the actual number of data bytes that can be
sent. If the WIT910 is using a protocol mode, the packet overhead does not need to be
considered. So in this example, the total capacity per remote would be:
44 bytes
25 ms = 14.08 kbps
It is also useful to remember that the asynchronous data input to the WIT910 is stripped
of its start and stop bits during transmission by the radio, yielding a "bonus" of 10/8 or
25% in additional capacity. Thus, 1.25 x 14.08 kbps = 17.6 kbps asynchronous. In actual
deployments, some allowance must be made for retransmissions of data, yielding a
throughput somewhat less than the calculated value.
The above calculations are provided as a means of estimating the capacity of a multipoint
WIT910 network. To determine the precise amount of capacity, you can actually set up
©2010-2015 by Murata Electronics N.A., Inc.
WIT910 Integration guide (R) 05/14/15
8 of 49
www.murata.com

WIT910
the radio system and then query the maximum data length from one of the remotes in
control mode to discover its exact setting. Divide this number by the hop duration as
above to get the remote's exact capacity.
2.2.5. Full Duplex Communication
From an application perspective, the WIT910 communicates in full duplex. That is, both
the user application and the remote terminal can be transmitting data without waiting for
the other to finish. At the radio level, the base station and remotes do not actually
transmit at the same time. If they did, the transmissions would collide. As discussed
earlier, the base station transmits a synchronization signal at the beginning of each hop
followed by a packet of data. After the base station transmission, the remotes will
transmit. Each base station and remote transmission may be just part of a complete
transmission from the user application or the remote terminal. Thus, from an application
perspective, the radios are communicating in full duplex mode since the base station will
receive data from a remote before completing a transmission to the remote.
2.2.6. Error-free Packet Transmission Using ARQ
The radio medium is a hostile environment for data transmission. In a typical office or
factory environment, 1% - 2% of the 900MHz frequency band may be unusable at any
given time at any given station due to noise, interference or multipath fading. For
narrowband radio systems (and also many spread spectrum radio systems which use
direct sequence spreading), this would imply a loss of contact on average of over 30
seconds per hour per station. The WIT910 overcomes this problem by hopping rapidly
throughout the band in a pseudo-random pattern. If a message fails to get through on a
particular channel, the WIT910 simply tries again on the next channel. Even if two thirds
of the band are unusable, the WIT910 can still communicate reliably.
Data input to the WIT910 is broken up by the radio into packets. A 24-bit checksum is
attached to each packet to verify that it was correctly received. If the packet is received
correctly, the receiving station sends an acknowledgment, or ACK, back to the transmitting
station. If the transmitter doesn't receive an ACK, at the next frequency hop it will attempt
to send the packet again. When ARQ is enabled, the transmitting radio will attempt to
send a packet packet attempts limit times before discarding the packet. A value of 00H
disables ARQ. When it is disabled, any transmission received with errors is discarded. It
is the responsibility of the user application to track missing packets. A second parameter,
ARQ Mode, allows the choice between using ARQ to resend unsuccessful transmissions
or always sending a transmission packet attempts limit times regardless of the success or
failure of any given transmission.
All of this error detection and correction is transparent to the user application. All the
user application sees is error-free data from the modem. However, if the ARQ mode is
disabled, transmissions with errors are discarded, and missing data detection will be the
©2010-2015 by Murata Electronics N.A., Inc.
WIT910 Integration guide (R) 05/14/15
9 of 49
www.murata.com

WIT910
responsibility of the user application. Refer to the Protocol Commands section for
complete details.
2.3 Modes of Operation
2.3.1. Control and Data Modes
The WIT910 has two modes of operation: Control mode and Data mode. When in
Control Mode, the various radio and modem parameters can be modified. When in Data
Mode, only data can be transmitted. The default mode is Data Mode. There are two
ways to enter Control Mode. The first way is to assert the Configure (CFG) pin on the
modem. Upon entering Control Mode, the modem will respond with a >prompt. After
each command is entered, the modem will again respond with a >prompt. As long as the
CFG pin is asserted, data sent to the modem will be interpreted as command data. Once
the CFG pin is de-asserted, the modem will return to Data Mode.
The second method for entering Control Mode is to send the escape sequence :wit2410
(all lower case) followed by a carriage return. In the default mode, the escape sequence is
only valid immediately after power up or after de-assertion of the Sleep pin on the
modem. The modem will respond in the same way with a >prompt. To return to Data
Mode, enter the Exit Modem Control Mode command, z>, or assert and de-assert the
Sleep pin. There are three modes for the escape sequence, controlled by the Set Escape
Sequence Mode command, zc:
zc = 0 Escape sequence disabled
zc = 1 Escape sequence available once at startup (default setting)
zc = 2 Escape sequence available at any time
The zc2 mode setting is useful if the user application has a need to change the modem
settings "on the fly". In this mode the escape sequence is always enabled and may be sent
at any time after a pause of at least 20ms. The modem will respond in the same way as
when in the default mode. It is necessary to issue the Exit Modem Control Mode
command, z>, before resuming data transmission.
Note: The escape sequence must be interpreted as data until the last character is received
and as such may be transmitted by the modem to any listening modems.
2.3.2. Sleep Mode
To save power consumption for intermittent transmit applications, the WIT910 supports a
Sleep Mode. Sleep Mode is entered by asserting the Sleep pin on the modem interface.
While in Sleep Mode, the modem consumes less than 250 µA. This mode allows the
radio to be powered off while the terminal device remains powered. After leaving Sleep
Mode, the radio must re-synchronize with the base station and re-register.
©2010-2015 by Murata Electronics N.A., Inc.
WIT910 Integration guide (R) 05/14/15
10 of 49
www.murata.com

WIT910
2.3.3. Low Power Mode and Duty Cycling
To conserve power, WIT910 remotes power down the receiver and transmitter between
hops when not in use. Base stations must remain active all the time to handle any
transmission from any remote. Remotes can save even more power by enabling the duty
cycle feature. This feature causes a remote to power down for 2Nfrequency hops where
1/2Nis the duty cycle. Rather than attempting to transmit on every frequency hop when
data is in the transmit buffer, a remote will attempt to transmit only every 2Nhops.
Roughly speaking, this will proportionately reduce the average power consumption while
increasing average latency. When there are more than 16 remotes being operated, duty
cycling must be enabled since a maximum of 16 time slots is available per hop.
When a remote radio is powered up but is out of range of a base station, it will
continuous scan the frequency bands for the presence of a base radio. During this
scanning the radio can consume up to 70 mA of current at 3.3-volts. The WIT910
employs a switching regulator so the current consumption will be less at higher voltages.
2.3.4. RF Flow Control Mode
Because of slight differences in baud rates between transmitting and receiving hosts,
when sending large amounts of data (100’s of KB) in one direction in a point-to-point
application, it is possible to overrun the receive buffer of the receiving radio. For example
a nominal 57.6Kbaud at the transmitting radio’s host might really be 57,601 and at the
receiving radio’s host it might be 56,599. This is similar to a situation where the
transmitting radio is sent data at a higher baud rate than the baud rate at which data is
received by the receiving host. To compensate for the variations in nominal baud rates,
the WIT910 supports an RF flow control mode for point-to-point operation. In this mode,
when the receive buffer of the receiving WIT910 is close to full, the receiving WIT910
stops acknowledging transmissions. The transmitting radio is set to infinite retries which
invokes the RF flow control mode (See Set Packet Attempts Limit in Section 5.3). The
receiving radio will not begin acknowledging transmissions from the transmitting radio
until more room in the receive buffer has become available. This will cause data in the
transmit buffer of the transmitting radio to back up. If it backs up to the point where the
transmit buffer fills up, the transmitting radio will deassert CTS stopping data from the
transmitting radio’s host device. Once room is available in the receiving radio’s buffer,
the receiving radio will begin acknowledging transmissions from the transmitting radio
allowing the transmitting radio’s buffer to begin to empty which will cause the
transmitting radio to reassert CTS. Either one or both of the radios in a point-to-point
installation can be configured for the RF flow control. If this mode is invoked in a point-
to-multipoint installation, communications with all radios will be stopped when any one
radio’s receive buffer becomes full.
©2010-2015 by Murata Electronics N.A., Inc.
WIT910 Integration guide (R) 05/14/15
11 of 49
www.murata.com

WIT910
3. PROTOCOL MODES
In point-to-point applications, it is generally desired that the radios operate in a
transparent mode. That is, raw unformatted data is sent from the host to the radio and is
received as raw data from the receiving end. The addressing and error detection and
correction are still performed by the radios, but it is transparent to the user application.
To set up a point-to-point network, one radio has to be set up as a base station. When the
radios are powered on, the base station will send out the synchronization signal at the
beginning of each hop. The remote will synchronize with the base and automatically
request registration. Once the remote is registered, the radios can transmit data. Protocol
mode operation is available in point-to-point mode if desired.
If the base station is to be responsible for directing data to a specific remote in point-to-
multipoint mode, the data sent to the base station by the user application must adhere to a
packet format. This allows transmissions from the base station to be directed to a specific
remote. Data received by a base station from a remote is similarly formatted to identify
to the user application the remote that sent the transmission. The remotes may still use
transparent mode without formatting to send data to the base, if desired. The WIT910
supports 10 protocol formats that are described in detail below. The protocol format is
selected through the Set Protocol Mode command.
Base and remote radios can use protocol modes to insure that a packet is transmitted to
the base without being broken up over multiple hops. The data length value in the data
packet becomes the effective minimum packet length and maximum packet length for that
packet. Note that if the remote data length is set to a number of bytes that is longer than
the number of bytes that can be transmitted by a remote on a single hop, the packet will
be discarded. For the base, this value is set by the Set Base Slot Size command. For
remotes this value is dynamically available through the Get Maximum Data Length
command or may be calculated based on the maximum number of remotes that can ever
be registered at one time. See Sections 5.3 and 2.2.3 respectively. Also note that using
protocol modes effectively disables Data Transmit Delay. This means that a packet will
not be transmitted until the entire packet has been sent to the radio, regardless of the
amount of time it takes.
If the remote hosts can determine what data is directed to them in point-to-multipoint
mode, the data can be sent to the base station without using a packet format. In this
situation, broadcast mode is selected at the base station by using the Set Default Handle
and selecting 3FH as the default handle. In this mode, the automatic retransmission of
unsuccessful transmissions is disabled. This is required since all of the remote modems
will attempt to acknowledge each base transmission when ARQ is enabled.
Transmissions that are received with errors are discarded by the radio. The remote
devices must be able to detect a missing packet and request a retransmission by the base
device.
©2010-2015 by Murata Electronics N.A., Inc.
WIT910 Integration guide (R) 05/14/15
12 of 49
www.murata.com

WIT910
Protocol Modes Definitions
mode 00 Transparent mode used for point-to-point networks
or multipoint remotes; does not support any packet
types.
mode 01 This is the simplest protocol mode supporting Data
packets only. This mode is not recommended for
base radios. No CONNECT or DISCONNECT
packets are supported and no sequence numbers are
provided.
packet types supported: Data
mode
02 This mode includes notification when remotes are
registered or dropped through CONNECT and
DISCONNECT packets that are sent to the user
application at the base station and at the remote. No
sequence numbers are provided.
packet types supported: Data
CONNECT
DISCONNECT
modes
03 – 08 reserved for future use.
mode 09 This mode sends the protocol mode 01 packets
during transmit but receives data transparently.
mode 0A This mode sends the protocol mode 02 packets
during transmit but receives data transparently.
modes 0C – 0F reserved for future use.
mode 11 This mode sends data transparently but supports
protocol mode 1 during reception.
mode 12 This mode sends data transparently but supports
protocol mode 2 during reception.
©2010-2015 by Murata Electronics N.A., Inc.
WIT910 Integration guide (R) 05/14/15
13 of 49
www.murata.com

WIT910
3.1 Packet Formats
The byte formats for each packet type are shown in the table below. Packet fields are
organized to fall on byte boundaries. In the case of bit-level fields, most-significant bits
are on the left.
MRTP (WIT910) packet types (modes 01-02):
Transmit and Receive:
Base DATA 1110 1001 00HH HHHH LLLL LLLL <0-188 bytes data>
Remote DATA 1110 1001 0000 0000 LLLL LLLL <0-212 bytes data>
Receive only:
CONNECT 1110 1001 10HH HHHH RRRR TTTT 00NN NNNN <3 byte remote
ID> DISCONNECT 1110 1001 11HH HHHH 0111 1111
H: handle number (0-63)
L: data length (0-188 for base, 0-212 for remote)
N: remote's previous network number (if roamed)
R: receive sequence number (from previous cell)
T: transmit sequence number (from previous cell)
Note that while the packet length can be set to 188, the maximum number of bytes
transmitted per hop is limited to the lesser of 188 or the length specified by maximum data
length. Packets with a data length longer than that will be discarded and not sent. See Get
Maximum Data Length for more details.
3.1.1. Data Packet
Modes 01 & 02:
Base 1110 1001 00HH HHHH LLLL LLLL <0-208 bytes data>
Remote 1110 1001 0000 0000 LLLL LLLL <0-212 bytes data>
This packet carries user data. The handle number is the handle of the receiving remote.
When data is being sent from a remote to the base, no handle number is required. Up to
212 bytes (188 for base radios) of user data may be carried per data packet but no more
than is specified by the maximum data length parameter. The radio will not break up a
packet over multiple hops. Packets with a data length greater than maximum data length
will not be sent and will be discarded. This parameter is variable and depends on the
number of remotes currently registered.
Handle 63 is reserved for broadcast packets from the base to all remotes.
Acknowledgment requests are not supported for broadcasts. For this reason, it is a good
idea to send broadcast messages several times to increase the odds of reaching all
remotes.
©2010-2015 by Murata Electronics N.A., Inc.
WIT910 Integration guide (R) 05/14/15
14 of 49
www.murata.com

WIT910
3.1.3. Connect Packet
1110 1001 10HH HHHH RRRR TTTT 00NN NNNN <3-byte remote ID> (base, receive
only)
H: handle number (0-62)
R: receive sequence number (from previous cell)
T: transmit sequence number (from previous cell)
N: network number of the previous base (if roamed)
1110 1001 10HH HHHH RRRR TTTT 00NN NNNN <3-byte base ID> (remote, receive
only)
H: handle number (0-62)
R: receive sequence number
T: transmit sequence number
N: network number of base
Remotes must go through an automatic registration process when roaming from one base
to another, after loss of contact, or when acquiring a base signal for the first time after
power up. The base then assigns the remote a handle value, may or may not assign it a
dedicated time slice depending on the user settings, and notifies the user application of
the new remote with a connect packet.
The network number of the last base the remote was connected to is given to aid user
software in resending orphan packets that may have been sent to the remote's previous
cell. If the remote has been powered up for the first time and this is the first base
contacted, the last base ID will be reported as 80H.
3.1.4. Disconnect Packet (base only, receive only)
1110 1001 11HH HHHH 0111 1111
H: handle number (1-62)
When a remote goes out of range or roams to another cell, the base issues a disconnect
packet to indicate that the remote is no longer available.
©2010-2015 by Murata Electronics N.A., Inc.
WIT910 Integration guide (R) 05/14/15
15 of 49
www.murata.com

WIT910
4. MODEM INTERFACE
Electrical connection to the WIT910 is made through a 16-pin male header on the modem
module. The signals are 3.3-volt signals and form an RS-232 style asynchronous serial
interface. The table below provides the connector pinout.
Pin Signal Type Description
1 GND - Signal and chassis ground
2 TXD Input Transmit data. Input for serial data to be transmitted. In Control
Mode also used to transmit modem commands to the modem.
3 RXD Output Receive data. Output for received serial data. In Control Mode,
also carries receive modem status from the modem.
4 Input
Configuration selector. Used to switch between Control and Data
Modes. Normally, CFG will be set for Data Mode. An internal 10K
pull-up enables Data Mode if this signal is left unconnected.
Control Mode is also accessible by transmitting an escape
sequence immediately after wake up or power up.
(0v) 1 = Control Mode
(3.3v) 0 = Data Mode
5 Input
Request to send. Gates the flow of receive data from the radio to
the user on or off. In normal operation this signal should be
asserted. When negated, the WIT2450 buffers receive data until
RTS is asserted.
(0v) 1 = Receive data (RxD) enabled
(3.3v) 0 = Receive data (RxD) disabled.
6 DTR Input Sleeps/wakes radio transceiver. In sleep mode all radio functions
are disabled. At wake up, any user programmed configuration
settings are refreshed from non-volatile memory, clearing any
temporary settings that may have been set.
(3.3v) 1 = Sleep Radio
(0v) 0 = Wake Radio
7 Output Data carrier detect. For remotes, indicates the remote has
successfully acquired the hopping pattern of the base station.
(0v) 1 = Carrier detected (synchronized)
(3.3v) 0 = No carrier detected (not synchronized)
8 Output Clear to send. Used to control transmit flow from the user to the
radio. (0v) 1 = Transmit buffer not full, continue transmitting
(3.3v) 0 = Transmit buffer full, stop transmitting
9 RSSI Output Received Signal Strength Indicator (analog signal)
10 Input Resets the radio.
11-15 - - Reserved for future use. Do not connect.
16 VCC - Positive supply. Min 3.3 v, 5.0 v nominal, 10.0 v max.
CFG
RTS
DCD
CTS
Reset
©2010-2015 by Murata Electronics N.A., Inc.
WIT910 Integration guide (R) 05/14/15
16 of 49
www.murata.com