Distech Controls ECLYPSE APEX, Руководство пользователя

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117 ECLYPSE APEX
These parameters are described in greater detail below.
Data Bus Segment MAC Address Range for BACnet MS/TP Devices
The BACnet MS/TP data bus supports up 255 devices:
£
Up to 128 devices (with device MAC addresses in the range of 0 to 127) that are BACnet MS/TP
Masters (that can initiate communication).
£
Up to 128 devices (with device MAC addresses in the range of 128 to 255) that are BACnet MS/
TP Slaves (cannot initiate communication).
However, it is recommended that any given data bus segment have no more than 50 devices, when a
baud rate of 19 200 or higher is used for the BACnet MS/TP Data Bus. A repeater counts as a device
on each data bus segment to which it is connected.
All Distech Controls’ devices are categorized as BACnet MS/TP Masters, that is, their device MAC ad-
dress can be set in the range of 0 to 127 only.
Device Loading
Each device presents an electrical load on the BACnet MS/TP Data Bus Segment. This is called de-
vice loading. The use of full load devices limits the number of devices connected to a BACnet MS/TP
Data Bus Segment to 32 devices. Distech Controls’ BACnet MS/TP devices are ⅛-load devices and
½-load devices, which allows more devices to be connected to the BACnet MS/TP Data Bus Segment,
as compared to full load devices.
Manufacturer Device load on the attached BACnet
MS/TP Data Bus
Distech Controls’ ECB and ECLYPSE Series controllers
Distech Controls’ ECB-PTU Series Line-Powered Controllers
⅛-load devices
Distech Controls’ BACnet MS/TP Thermostats ½-load devices
Other manufacturers Refer to their documentation
Table 11: Device Loading
However, if a data bus segment is interoperating with devices that are full-load, ½-load, ¼-load, or ⅛-
load, then the device that supports the fewest devices on the same data bus is the one that sets the
limit for the maximum total number of devices for that data bus segment. For example, you plan to put
on one data bus the following devices:
Manufacturer Quantity of de-
vices (example)
Equivalent full-
load devices
Maximum devices supported by the
manufacturer
Distech Controls’ devices (⅛-load
devices)
8 1 128 1 Maximum 50 recommended
Distech Controls’ BACnet MS/TP
Thermostats (½-load devices)
14 7 64 Maximum 50 recommended
Manufacturer Y (full load devices) 26 26 32
Total Full-Load Devices 34
There are too many devices on the data
bus. It is limited to a maximum of 32
devices by Manufacturer’s Y devices.
Table 12: Device Loading Example
1. This is limited by the maximum number of master devices allowed on a BACnet MS/TP Data Bus.
The solution for the above example is to create two data bus segments connected together by a re-
peater and then split up the devices between the data bus segments, ensuring again that the maxi-
mum number of devices on each separate data bus is not exceeded. See
Using Repeaters to Extend
the Data Bus .
BACnet MS/TP Communication Data Bus Fundamentals