Murata Electronics North America DNT500FP Manual Do Utilizador
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DNT900 - 11/05/08
Once a remote has synchronized with the base station, it will request registration information to allow it to
join the network. Registration can be handled automatically by the base station, or it can be controlled by
allowing the base station host application to authenticate the remote for registration. When a remote is
registered, it receives several network parameters from the base station, including HopDuration, InitialN-
wkID
join the network. Registration can be handled automatically by the base station, or it can be controlled by
allowing the base station host application to authenticate the remote for registration. When a remote is
registered, it receives several network parameters from the base station, including HopDuration, InitialN-
wkID
, FrequencyBand and Nwk_Key (see Section 4.2 for parameter details). Note that if a registration
parameter is changed at the base station, it will update the parameter in the remotes over the air.
Among other things, registration allows the tracking of remotes entering and leaving a network, up to a
limit of 254 remotes. The base station builds a table of serial numbers of registered remotes using their
three-byte serial numbers (MAC addresses). To detect if a remote has gone offline or out of range, the
registration is “leased” must be “renewed” once every 250 hops. Any transmission from a remote running
on a leased registration will renew its lease with the base station.
limit of 254 remotes. The base station builds a table of serial numbers of registered remotes using their
three-byte serial numbers (MAC addresses). To detect if a remote has gone offline or out of range, the
registration is “leased” must be “renewed” once every 250 hops. Any transmission from a remote running
on a leased registration will renew its lease with the base station.
2.2 Transparent and Protocol Serial Port Modes
DNT500 radios can work in two serial port data modes: transparent and packet protocol. Transparent
mode formatting is simply the raw user data. Protocol mode formatting includes a start of packet framing
character, length byte, addressing, command bytes, etc. Transparent mode operation is especially useful
in point-to-point systems that act as simple cable replacements. In point-to-multipoint systems where the
base station needs to send data specifically to each remote, protocol formatting must be used. Protocol
formatting is also required for configuration commands and responses, and sensor I/O commands and
responses. Protocol formatting details are covered in Section 4.
mode formatting is simply the raw user data. Protocol mode formatting includes a start of packet framing
character, length byte, addressing, command bytes, etc. Transparent mode operation is especially useful
in point-to-point systems that act as simple cable replacements. In point-to-multipoint systems where the
base station needs to send data specifically to each remote, protocol formatting must be used. Protocol
formatting is also required for configuration commands and responses, and sensor I/O commands and
responses. Protocol formatting details are covered in Section 4.
The DNT500 provides two ways to switch between transparent and protocol modes. If CFG input Pin 18
on the DNT500 is switched from logic high to low, protocol mode is invoked. Or if the ASCII escape
sequence “DNT500” is sent (without quotation marks) to the primary serial input following at least a 20 ms
pause in data flow, the DNT500 will switch to the protocol mode. When input Pin 18 is switched from logic
low to high, or an ExitProtocolMode command is sent to the primary serial input, the DNT500 will switch
to transparent operation. Note that if the escape sequence is used to switch to protocol mode, the se-
quence will be transmitted before protocol mode is invoked.
on the DNT500 is switched from logic high to low, protocol mode is invoked. Or if the ASCII escape
sequence “DNT500” is sent (without quotation marks) to the primary serial input following at least a 20 ms
pause in data flow, the DNT500 will switch to the protocol mode. When input Pin 18 is switched from logic
low to high, or an ExitProtocolMode command is sent to the primary serial input, the DNT500 will switch
to transparent operation. Note that if the escape sequence is used to switch to protocol mode, the se-
quence will be transmitted before protocol mode is invoked.
When operating in transparent mode, two configuration parameters control when a DNT500 radio will
send the data in its transmit buffer. The MinPacketLength parameter sets the minimum number of bytes
that must be present in the transmit buffer to trigger a transmission. The TxTimeout parameter sets the
maximum time data in the transmit buffer will be held before transmitting it, even if the number of data
bytes is less than MinPacketLength. The default value for both the MinPacketLength and the TxTimeout
parameters is zero, so that any bytes that arrive in the DNT500 transmit buffer will be sent on the next
hop. As discussed in Section 2.5.2, it is useful to set these parameters to non-zero values in point-to-
multipoint systems where some or all the remotes are in transparent mode.
send the data in its transmit buffer. The MinPacketLength parameter sets the minimum number of bytes
that must be present in the transmit buffer to trigger a transmission. The TxTimeout parameter sets the
maximum time data in the transmit buffer will be held before transmitting it, even if the number of data
bytes is less than MinPacketLength. The default value for both the MinPacketLength and the TxTimeout
parameters is zero, so that any bytes that arrive in the DNT500 transmit buffer will be sent on the next
hop. As discussed in Section 2.5.2, it is useful to set these parameters to non-zero values in point-to-
multipoint systems where some or all the remotes are in transparent mode.
2.3 RF Data Communications
At the beginning of each hop, the base station transmits a synchronizing signal. After the synchronizing
signal is sent, the base will transmit any user data in its transmit buffer, unless in transparent mode the
MinPacketLength
signal is sent, the base will transmit any user data in its transmit buffer, unless in transparent mode the
MinPacketLength
and/or TxTimeout parameters have been set to non-zero. The maximum amount of
data that the base station can transmit per hop is limited by the BaseSlotSize parameter, which has a
maximum value of 233 bytes. If there is no user data or reception acknowledgements (ACKs) to be sent
on a hop, the base station will only transmit the synchronization signal.
maximum value of 233 bytes. If there is no user data or reception acknowledgements (ACKs) to be sent
on a hop, the base station will only transmit the synchronization signal.