Murata Electronics Corporation 5 6/2/2021
the base station can transmit per hop is determined by the base slot size parameter. The
maximum amount of data sent by a base station per hop is 192 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 WIT2420 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 192 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 also
be set, which force the remote to wait until a certain amount of data is available or the
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