N2 (M5.8.3) - Siemens bt300 Operator's Manual

Chapter 4 - Parameters and Menu Structure
I/O and Hardware (M5)
Structure Parameter
P5.8.1.1 Protocol

N2 (M5.8.3)

The N2 communications protocol is used by Johnson Controls and others to connect terminal unit controllers to
supervisory controllers. It is open to any manufacturer and based upon a simple ASCII protocol widely used in the
process control industry.
The physical characteristics of the N2 bus
4,000 foot distance, running at 9,600 bps. Logically, the N2 is a master-slave protocol; the supervisory controller is
normally the master. Data is partitioned into common HVAC control objects, such as analog input, analog output,
binary input, and binary output. N2 messaging supports the reading, writing, and overriding of these points.
Additionally, there are messages defined to perform uploads and downloads of devices as well as to direct
memory reads and writes.
The N2 fieldbus protocol supports the following point types:
● Analog Input (AI)
● Analog Output (AO)
● Binary Input (BI)
● Binary Output (BO)
● Internal Integer (ADI)
If Protocol (P5.8.1.1) is set to a value of N2, then configuration and status parameters related to the N2 fieldbus
protocol are made available as listed in the Parameters and Monitoring sections below.
Parameters (M5.8.3.1)
The following configuration parameters are available for the N2 fieldbus protocol:
Menu Parameter
P5.8.3.1.1 Device Address
P5.8.3.1.2 Communications Timeout
118 | 180
Siemens Industry, Inc.
Building Technologies
Table 87: Common Settings.
Min. Max.
No Protocol Modbus RTU
is
an RS-485 3wire connection
Table 88: N2 Protocol Parameters.
ID Unit
2350
2351 s
Siemens BT300 HVAC Drive
Default ID
No Protocol 2208
,
with a maximum of 100 devices over a
Mn. Max. Default
1 255 1
0 255 10
Description
Defines the RS-485 base fieldbus protocol to
be used:
0 = No Protocol
1 = N2
2 = BACnet MS/TP
3 = P14 = Modbus RTU
NOTE: A new menu will be accessible at
M5.8.3 depending upon the protocol selected.
Configuration for protocol communications will
be within that menu.
NOTE: This selection enables monitoring only.
If control (start/stop and speed reference) is to
be from fieldbus, then Ctrl. Place Auto (P3.3.1)
must be set to FieldbusCTRL.
Description
Defines the unique slave address to be
used by the drive on the N2 network.
Defines the amount of time in which a
packet is not received before a
communications timeout is faulted/alarmed.
DPD01809
2016-06-07