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CCT24
The
InitialParentNwkID
parameter controls which parent a child router or remote can join. Setting this
value to 0x00 forces a router or a remote to join with only the base. Setting this parameter to the
NwkID
of
a parent router forces a child router or a remote to join only this parent’s network. Setting this parameter
to 0xFF in a router or remote allows them to join with any parent.
The
StaticNetAddr
parameter controls the assignment of the
NwkAddr
byte in a remote’s system address.
A remote’s
NwkAddr
can be manually assigned by setting the
StaticNetAddr
to a value between 0x01 and
0x7E. Setting the
StaticNetAddr
parameter to 0xFF allows the remote’s parent to dynamically assign a
NwkAddr
.
As discussed above, an example CCT24 tree-routing system is shown in Figure 2.12.1.2. The example
system includes remote R4 which is directly linked to the base, routers R2 and R5 which are directly
linked to the base, remotes R1 and R3 which are linked to router R2, remote R7 which is linked to router
R6, which in turn is linked to router R5. The parent network ID, the system address and for routes the
base-mode network ID are shown in hexadecimal format.
Note that when dynamic address assignment is used, the system addresses of some of the radios in the
system will not be immediately apparent. A radio’s system address can be obtained by broadcasting a
Discover
command from the base which contains the radio’s hardware MAC address. The radio will send
a
DiscoverReply
with its system address. After joining one of the system networks, all routers and re-
motes periodically transmit heartbeat status messages that contains their MAC address, network address,
network ID and other information. Note that the address of any radio can be constructed as follows:
0xFF + NwkID + NwkAddr.
2.12.4 Tree-Routing System Implementation Options
There are three ways to assign parent network IDs and system addresses to the routers and remotes in a
tree-routing system - dynamic router parent and remote system address assignment, manual router
parent assignment with dynamic remote address assignment, and manual router parent and remote
address assignment.
Dynamic router parent and remote address assignment is the preferred method for most systems that
contain just a few routers. This assignment method provides several advantages. The router parent and
remote system addresses do not have to be pre-assigned, reducing initial system planning details. In
case of a parent failure, child devices will automatically attempt to join another parent. Once the system
becomes organized, heartbeat status messages and/or Discover commands can be used to log the
system addresses against the MAC addresses of each router and remote in the system.
Manual router parent assignment with dynamic remote address assignment is the preferred method for
most systems with a large number of routers. Manual router parent assignment avoids the possibility of
the system creating a long chain of parent router-child router links which would introduce unnecessary
message latency. However, manual router assignment precludes a child router from attempting to link
with another parent in case its parent router fails. The parent address of each router is known before the
system becomes organized, and heartbeat status messages and/or
Discover
commands can be used to
log the system addresses against the MAC addresses of each remote in the system.
Manual router parent and remote address assignment allows all radios addressing to be preplanned and
preset before a system is installed. Manual system addressing precludes child radios from attempting to
re-link to the system by joining another parent if the assigned parent fails, but simplifies application code
