MERLIN NX IP AND MST/TP VAV CONTROLLER - INSTALLATION INSTRUCTIONS
23
EN1Z-1076GE51 R0722
BACNET MSTP CONTROLLER
Automatic MAC Addressing
In contrast to other controllers, the MERLIN NX MSTP
controllers feature automatic MAC addressing.
NOTE:
Automatic MAC addressing will be enabled only if dip
switches are all-on or all-off.
The MAC addresses are not assigned in sequential order.
Controllers are assigned MAC addresses that are not
already in use by another BACnet MSTP device in the
range of Min MAC to Max MAC.
In the scenario depicted in
, some of the controllers
in the BACnet MSTP network do not feature automatic
MAC addressing; therefore, their MAC addresses are
assigned manually. Thus, when a new MERLIN NX BACnet
MSTP VAV is added to the network and its automatic MAC
addressing function is triggered, it will assign itself an
available (unused) MAC address within the range of Min
MAC and Max MAC values.
Fig. 29. Automatic MAC addressing
All MERLIN NX MSTP VAV controllers are BACnet MSTP
clients. Every client performs periodic polling for the
possible appearance of new clients. Each client knows the
identity of the next client on the BACnet MSTP bus and to
which it must pass the token. The polling process includes
searching for new clients with MAC addresses lying
between their own MAC address and that of the next client.
The property maxMaster specifies the highest-allowable
address for master nodes. The maxMaster is set to 64 by
default, thus guaranteeing that, on a BACnet MS/TP bus
with, for example, 35 BACnet MSTP VAV controllers, all of
the other BACnet MSTP VAV controllers will be found.
Following properties are writable and can be changed:
— maxMaster
— min MAC
— max MAC
— MAC address
NOTE:
You should not attempt to program a MAC Address
outside the range of min MAC and max MAC (1 to
64)
Manual configuration of the MAC
Address
The MS/TP MAC address for each device must be set to a
unique value in the range of 1-64 on an MS/TP network
segment (address 0, 1, 2, & 3 should be avoided as they
are commonly used for the router, diagnostic tools, and as
spare addresses). A seven position DIP switch on the
MERLIN NX MS/TP BACnet controller is used to set the
controller's MAC address.
NOTE:
DIP setting of all-ON or all-OFF will enable the Auto
MAC mode in controller and the dip switches will not
be used for MAC addressing.
See “Automatic MAC
Addressing” on page 24.
To set the MS/TP MAC address of a MERLIN NX BACnet
MSTP VAV controller:
Default
maxmaster
Default
MinMAC
Default
MaxMAC
Default Baud
rate
64
1
60
38400
1
4
3
2
5
7
6
ON
1
4
3
2
5
7
6
ON
All ON
All OFF
