Model 9060Z Manual
APPENDIX 4, MODBUS™
The Teledyne Analytical Instruments 9060Z transmitter has the ability to work as a Modbus slave node on serial RS‐232 or 3‐wire RS‐485 via RTU mode transmissions. By accessing information stored in the input and holding registers it is possible to access runtime variables, alarm conditions and modify the device configuration.
The implementation of the Modbus protocol is limited to the specific command set relevant to reading and writing register variables. Attempting to send unrecognised commands will result in appropriate error responses
MODBUS™ Functions Supported:‐ |
|
0x03: Read Holding Registers | 0x16: Mask Write Holding Register |
0x04: Read Input Registers | 0x17: Read/Write Multiple Holding Registers |
0x06: Write Single Holding Register | 0x2B: Encapsulated Interface (read device |
0x08: (return query data – for loopback testing) | information) |
0x10: Write Multiple Holding Registers | 0x41: Special Instruction Function |
Serial Configuration
The serial configuration for the slave device is accessed in the Commissioning menu of the transmitter. Default settings are highlighted in bold.
Baud Rate | 9600, 19200, 38400, 57600 |
Parity | Even, Odd, None |
Stop Bits | 1 |
Interface | RS‐485, RS‐232 |
All holding register addresses contain a single 16 bit value, however some variables span multiple holding registers to yield a single 32 bit variable.
When reading register values be aware that the byte order of data within registers may differ from that of the target system.
Modbus Protocol
The modbus over serial line protocol defines a messaging system for master/slave communications. Only one master device may be connected to any network with one or several slave nodes.
In unicast mode, the master initiates communication with a specific slave node by sending a request message. The slave processes the request and returns a reply message containing the requested information or a confirmation that the request was fulfilled.
Modbus requests are transmitted as a formed request frame with a CRC for data integrity checking. The frame for each request and reply type will vary somewhat, but will always have the basic structure described below:
1 byte | 1 byte | up to 255 bytes | 2 bytes |
slave address | function code | data | checksum |
Internal Representation of Dates & Alarm Status
The transmitter stores all dates as an unsigned 32bit count of seconds elapsed since 1‐Jan 2004.
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