Linx Technologies TRM-915-R250 - Manual (Page 11)

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User Networking Mode
User Networking Mode is a more complicated scheme than GUID
mode. It uses the customer ID bytes (regCUSTID[0-1]) and two of the
user destination bytes (regUSERDESTID[0-1]) as a destination address.
The customer ID bytes are programmed at the factory and cannot be
changed. The module’s local address is contained in two of the user
source ID registers (regUSERSRCID[0-1]). Each module also has a user ID
mask (regUSERIDMASK[0-1]) that provides an additional logical layer of
addressing and can be used to create sub-networks. The receiving module
masks its local address and the received destination address by calculating
the logical AND with the user ID mask. If the results are equal, then the
payload is output on the UART. The customer ID bytes are not masked, but
must match the local value.
If acknowledgements are enabled, only the module with a user source ID
that matches the transmitted user destination ID responds. The mask is not
used for this determination.
If the result of the user ID Mask AND the received user destination address
equals the same value as the user ID mask, then the payload data is output
on the UART. This acts as a broadcast message to the network.
Setting the mask to 0xFFFF removes the mask and only the source and
destination addresses are used for networking. When using user network
mode to send packets to multiple users and the mask is not equal to
0xFFFF, acknowledgements must be disabled. Failure to do so could cause
extreme delays in transmission and loss of data.
As an example, if the mask is 0xFFF0 and the destination address
transmitted by the sender is 1234, then all modules with a source ID of
123x respond. This gives a subnet of 16 modules (where x = 0 to F) and
acts as a broadcast message to the sub-net. Acknowledgements should
be disabled.
Figure 14 shows this example and Figure 12 and Figure 13 show some
more examples of user networking mode.
Figure 12: 250 Series Transceiver User Network Mode Examples
250 Series Transceiver User Network Mode Examples
Destination
ID from
Received
Packet
Receiver
Source
ID
Receiver
User ID
Mask
Result of
Dest
AND
Mask
Result of
Source
AND
Mask
Action
3000
2000
E000 2000
2000
The results are equal, so
the payload is output on
the UART.
3000 2000
The results are equal, so
the payload is output on
the UART. The destination
ID and the source ID
match, so an ACK is
transmitted if enabled.
4000 4000
The results do not match,
so the packet is discarded.
3000
2000
F000 3000
2000
The results do not match,
so the packet is discarded.
3000 3000
The results are equal, so
the payload is output on
the UART. The destination
ID and the source ID
match, so an ACK is
transmitted if enabled.
4000 4000
The results do not match,
so the packet is discarded.
E000
2000
E000 E000
2000
The destination ID matches
the user ID mask, so the
data is output on the UART.
3000 2000
4000 4000
250 Series Transceiver User Network Mode Examples
Sender Receiver
Network
Mode
User
SRCID
User
DESTID
User
SRCID
User
IDMASK Response
0x06
(User)
0x1000 0xFFFF
0x2000 0XFFFF Data output by both modules. No
ACK sent by either module. 0x3000 0xFFFF
0x16
(User +
ACK)
0x1000 0xFFFF
0x2000 0xFFFF Data output by both modules. No
ACK sent by either module. This
configuration causes transmission
problems.
0x3000 0xFFFF
0x16
(User +
ACK)
0x1000 0x3000
0x2000 0xE000 Data output. No ACK sent.
0x3000 0xE000
Data output. ACK sent to
0x1000.
0x6
(User)
0x1000 0x3000
0x2000 0xF000 Not processed – discarded.
0x3000 0xF000 Data output. No ACK sent.
Figure 13: 250 Series Transceiver User Network Mode Examples