OM-CP-RF Series Operations Manual
Omega Engineering, Inc.
Revised 04/07/05
Page 13 of 18
node address within that system. Most applications will us a module address of the format
XXYY, where XX is the system number and YY is the node address. A system is comprised of
a PC connected to an RFExtender transceiver (the “Local Node”) and several other
transceivers (“Remote Nodes”) set up within the transmission range. Using the system
number is not strictly necessary, but it allows several groups of transceivers to be located
within transmission distance of each other without allowing data from one group to be
received by the other.
The receiver address mask is also 4 digits and will usually be configured in one of two
ways: to receive data from all the modules within a system, or to receive data only from
another module with the same module address. Only the local node at the PC will be
configured to receive from multiple modules, as only the PC is capable of receiving and
processing the data being transmitted by all the modules. The remote nodes will be
assigned individual addresses, and configured only to accept transmissions from a module
with the same address as their own. To allow two-way communication with a remote node,
the local node module address and receiver address mask will be changed temporarily to
match that of the remote node.
Assigning module addresses should begin with the determination of the system number.
The system numbers used may be sequential, starting with one, as the zero address has
special significance. The local node should be assigned node address zero, and the remote
nodes may be sequential starting with one. Note that this is how the module addresses in
Figure 6 were generated.
The receiver address mask instructs the transceiver which data to receive by indicating
what part of the incoming module address should be compared to its own module address.
The remote nodes should be assigned receiver address masks of “FFFF”. In general terms, a
hexadecimal digit “F” in the receiver address mask means “compare this digit”. So a
receiver address mask of “FFFF” means “compare all the digits”, and if all the digits do not
match, ignore the incoming data. In technical terms, the comparison is performed as a
logical “AND” operation, which is a common function in computers and digital circuits.
The local node in Figure 6 is assigned an address mask of “FF00”. This can be
interpreted as “compare the system number, but not the node number”. (Technically, the
“AND” function will always result in a node address of “00”.) This way, the PC will receive
data from all the transceivers in its system.
Receiver Address Mask Example
The local node in Figure 6 has a module address of “0100” and a receiver address mask
of “FF00”. Suppose that it receives data from module address “0104”. The incoming address
is processed through the mask as “0104” AND “FF00” = “0100”. The result matches the
local node address of “0100”, so the transceiver passes the data through.
Likewise, suppose that module address “0104” receives data from module address
“0108”. The incoming address is processed through the mask as “0108” AND “FFFF” =
“0108”. The result does not match the receiver’s module address of “0104”, so the receiver
ignores the data.
For further information on uses of the module address and receiver address mask,
contact Omega Technical Support.
Summary of Contents for OM-CP-RF Series
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