Johnson Controls N2-Bus
Johnson Controls N2-Bus protocol
Supported device types and versions
Communication line configuration
Communication station configuration
Station parameters
I/O tag configuration
Time Schedules configuration
Literature
Changes and modifications
Document revisions
Supported device types and versions
This protocol supports data reading from/writing to Johnson Controls devices - DX9100 series units, that are equipped with a serial port for N2 Bus. The implementation currently does not support the N2 Open standard.
Communication line configuration
Categories of communication line: Serial, SerialOverUDP Device Redundant, RFC2217 Client, TCP-IP/TCP.
Transmission parameters N2 Bus, usually set to 9600 Baud, 8 data bits, no parity, 1 stop bit.
Note: on TCP-IP/TCP line, multiple hostnames or IP addresses separated by comma/semicolon can be defined to connect to multiple devices in a round-robin fashion.
Communication station configuration
Communication protocol: Johnson Controls N2-Bus.
The address of the station on N2 Bus is the number in the range of 1 to 255, the address 0 is reserved.
Reading of object values on the station is executed periodically according to time parameters "Polling parameters".
The synchronization of real-time can be activated - check the Enable parameter in the "Synchronization period" section and set the period, which defines a period of writing a real-time.
Station parameters
The configuration dialog box - Parameters tab.
The parameters influence some optional parameters of the protocol. There can be defined the following parameters of station protocol:
Table 1
Parameter | Meaning | Unit | Default value |
|---|---|---|---|
Wait Timeout | The delay between reading the responses until it is completed. | ms | 100 ms |
Wait First Timeout | The first waiting for a response after sending a request. | ms | 200 ms |
Retry Timeout | The delay between request retries if a communication error occurs. | ms | 500 ms |
Max. Wait Retry | The number of readings of a response until it is completed. | - | 10 |
Retry Count | The number of request retries when an error in communication occurs. | 1 .. 32 | 2 |
Max Errors | The maximum number of consecutive errors in one station reading cycle after which the next I/O tags are no longer read. A value of 0 causes all I/O tags to be read. | - | 0 |
Full Debug | Enables the detailed debug information about the values of I/O tags that were obtained by polling. | YES/NO | NO |
I/O tag configuration
Used I/O tags: Ai, Ao, Ci, Co, Di, Dout.
The address of the I/O tag can be defined in two formats:
1. Predefined items of DX9100 have format:
Modul.Tag
Where Modul is the name of the module and Tag is the name of the tag within a module. The list of items is based on the documentation DX-9100 Configuration Guide, Appendix B. Since this is a large list of the static items, an "Object Browser" dialog window is prepared, where you may find the particular object. In the "Item Address" section click the button next to the "Item" field.
The following window opens:
The left part of the window contains the list of modules. After clicking the particular module, the list of tags that belong to this module is displayed in the right part of the window.
Parameters of items:
Tag: Name of the tag.
Description: Short description of the item.
Access: Access level (R - read-only, R/W - read and write, CNF - read and write, the configuration parameter is stored into EEPROM).
Type: Value type of item (see also here).
Address: Physical address of item that is used for reading/writing. It is calculated from the starting address of the module and offset tag (in hexadecimal format). The bit number (1 up to 32) of the addresses of binary items is placed after the dot.
After double-clicking a selected tag, the dialog window is closed and the name of the item is copied in the "Item" field in the "Item Address" section.
2. User format:
#Typ.Addr[.Bit]