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CHAPTER 4: SETPOINTS
DEVICE
889 GENERATOR PROTECTION SYSTEM – INSTRUCTION MANUAL
4–23
Communications
The 8 Series relays have a two-stage communications capability. The base CPU supports
Modbus protocol through the Ethernet, USB, serial and WiFi port. In addition, the base CPU
also supports IEC 103, DNP serial, DNP TCP/IP, and TFTP protocol. Once the
communications module option is added to the base, the base Ethernet port becomes
disabled but the two Ethernet ports on the communications module have enhanced
communications capabilities such as IEC61850, IEC62439 parallel redundancy protocol
(PRP) and IEEE 1588 Precision Time Protocol (PTP). The communications CPU also supports
Modbus TCP, IEC 104, DNP TCP, TFTP, SFTP, and SNTP protocol.
Modbus Protocol
All Ethernet ports and serial communication ports support the Modbus protocol. The only
exception is if the serial port has been configured for DNP or IEC 60870-5-103 operation
(see descriptions below). This allows the EnerVista 8 Series Setup software (which is a
Modbus master application) to communicate to the 889.
The 889 implements a subset of the Modicon Modbus RTU serial communication standard.
The Modbus protocol is hardware-independent. That is, the physical layer can be any of a
variety of standard hardware configurations. This includes USB, RS485, fiber optics, etc.
Modbus is a single master / multiple slave type of protocol suitable for a multi-drop
configuration.
The 889 is always a Modbus slave with a valid slave address range 1 to 254.
DATA FRAME FORMAT AND DATA RATE
One data frame of an asynchronous transmission to or from an 889 typically consists of 1
start bit, 8 data bits, and 1 stop bit. This produces a 10-bit data frame. This is important for
transmission through modems at high bit rates. Modbus protocol can be implemented at
any standard communication speed. The 889 supports operation at 9600, 19200, 38400,
57600, and 115200 bps baud rate. The USB interface supports ModBus TCP/IP.
FUNCTION CODE SUPPORTED
The following functions are supported by the 889:
•
FUNCTION CODE 03H - Read Setpoints
•
FUNCTION CODE 04H - Read Actual Values
•
FUNCTION CODE 05H - Execute Operation
•
FUNCTION CODE 06H - Store Single Setpoint
•
FUNCTION CODE 07H - Read Device Status
•
FUNCTION CODE 08H - Loopback Test
•
FUNCTION CODE 10H - Store Multiple Setpoints
•
FUNCTION CODE 42H - Group Settings Read
•
FUNCTION CODE 43H - Group Settings Write
When a ModBus master such as the EnerVista 8 Series Setup software communicates to
the 889 over Ethernet, the 889 slave address, TCP port number and the 889 IP address for
the associated port must be configured and are also configured within the Master for this
device. The default ModBus TCP port number is 502.
The following ModBus parameters are configurable:
Path:
Setpoints > Device > Communications > Modbus Protocol