Murata Electronics North America DNT500FP Manual Do Utilizador
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©2008 by RF Monolithics, Inc.
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DNT900 - 11/05/08
The operation for remotes is similar to the base station, but without the synchronizing signal. The Re-
moteSlotSize
moteSlotSize
parameter sets the maximum number of bytes a remote can transmit on one hop, up to a
limit of 243 bytes per hop. The RemoteSlotSize must be coordinated with the HopDuration and BaseSlot-
Size
Size
parameters and the number of registered remotes. The MinPacketLength and TxTimeout parame-
ters operate in a remote in the same manner as in the base station.
2.4 RF Transmission Error Control
The DNT500 supports two error control modes: automatic transmission repeats (ARQ), and redundant
transmissions for broadcast packets from the base station. In both modes, the radio will detect and dis-
card any duplicates of messages it receives so that the host application will only receive one copy of a
given packet. In the redundant transmission mode, broadcast packets are repeated a fixed number of
times based on the value of the ARQ_AttemptLimit parameter. In ARQ mode, a packet is sent and an
acknowledgement is expected on the next hop. If an acknowledgement is not received, the packet is
transmitted again on the next available hop until either an ACK is received or the maximum number of
attempts is exhausted. If the ARQ_AttemptLimit parameter is set to its maximum value, a packet trans-
mission will be retried without limit until the packet is acknowledged. This is useful in some point-to-point
cable replacement applications where it is important that data truly be 100% error-free, even if the desti-
nation remote goes out of range temporarily.
transmissions for broadcast packets from the base station. In both modes, the radio will detect and dis-
card any duplicates of messages it receives so that the host application will only receive one copy of a
given packet. In the redundant transmission mode, broadcast packets are repeated a fixed number of
times based on the value of the ARQ_AttemptLimit parameter. In ARQ mode, a packet is sent and an
acknowledgement is expected on the next hop. If an acknowledgement is not received, the packet is
transmitted again on the next available hop until either an ACK is received or the maximum number of
attempts is exhausted. If the ARQ_AttemptLimit parameter is set to its maximum value, a packet trans-
mission will be retried without limit until the packet is acknowledged. This is useful in some point-to-point
cable replacement applications where it is important that data truly be 100% error-free, even if the desti-
nation remote goes out of range temporarily.
2.5 Network Configurations
The DNT500 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, each
communication takes place between the base station and one of the remotes. Remotes cannot communi-
cate directly with each other. It should be noted that point-to-point operation is a subset of the point-to-
multipoint operation, so there is no need to specify one or the other.
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, each
communication takes place between the base station and one of the remotes. Remotes cannot communi-
cate directly with each other. It should be noted that point-to-point operation is a subset of the point-to-
multipoint operation, so there is no need to specify one or the other.
2.5.1 Point-to-Point Network Operation
Most point-to-point networks act as serial cable replacements and both the base station and the remote
use transparent mode. Unless the MinPacketLength and TxTimeout parameters have been set to non-
zero, the base station will send the data in its transmit buffer on each hop, up to a limit controlled by the
BaseSlotSize
use transparent mode. Unless the MinPacketLength and TxTimeout parameters have been set to non-
zero, the base station will send the data in its transmit buffer on each hop, up to a limit controlled by the
BaseSlotSize
parameter. In transparent mode, if the base station is buffering more data than can be sent
on one hop, the remaining data will be sent on subsequent hops. The base station adds the address of
the remote, a packet sequence number and error checking bytes to the data when it is transmitted. These
additional bytes are not output at the remote in transparent mode. The sequence number is used in
acknowledging successful transmissions and in retransmitting corrupted transmissions. A two-byte CRC
and a one-byte checksum allows a received transmission to be checked for errors. When a transmission
is received by the remote, it will be acknowledged if it checks error free. If no acknowledgment is re-
ceived, the base station will retransmit the same data on the next hop. Note that acknowledgements from
remotes are suppressed on broadcast packets from the base station.
the remote, a packet sequence number and error checking bytes to the data when it is transmitted. These
additional bytes are not output at the remote in transparent mode. The sequence number is used in
acknowledging successful transmissions and in retransmitting corrupted transmissions. A two-byte CRC
and a one-byte checksum allows a received transmission to be checked for errors. When a transmission
is received by the remote, it will be acknowledged if it checks error free. If no acknowledgment is re-
ceived, the base station will retransmit the same data on the next hop. Note that acknowledgements from
remotes are suppressed on broadcast packets from the base station.
In point-to-point operation, by default a remote will send the data in its transmit buffer on each hop, up to
the limit controlled by its RemoteSlotSize parameter. If desired, the MinPacketLength and TxTimeout
parameters can be set to non-zero values, which configures the remote to wait until the specified amount
of data is available or the specified delay had expired before transmitting. In transparent mode, if the
the limit controlled by its RemoteSlotSize parameter. If desired, the MinPacketLength and TxTimeout
parameters can be set to non-zero values, which configures the remote to wait until the specified amount
of data is available or the specified delay had expired before transmitting. In transparent mode, if the