Tyco 1540 - Manual (Page 59)

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Integra 1540, 1000, 0640, 0440, 0340, 0240 Issue 1 04/03
The data format in RTU mode is:
Coding System: 8-bit per byte
Data Format: 4 bytes (2 registers) per parameter.
Floating point format ( to IEEE 754)
Most significant register first (Default). The default may be changed if
required - See Holding Register "Register Order" parameter.
Error Check Field: 2 byte Cyclical Redundancy Check (CRC)
Framing: 1 start bit
8 data bits, least significant bit sent first
1 bit for even/odd parity or no parity
1 stop bit if parity is used; 1 or 2 bits if no parity
Data Transmission speed is selectable between 2400, 4800, 9600 and 19200 baud.
Input Registers
Input registers are used to indicate the present values of the measured and calculated electrical
quantities.
Each parameter is held in two consecutive 16 bit registers. The following table details the 3X
register address, and the values of the address bytes within the message. A tick (÷) in the
column indicates that the parameter is valid for the particular wiring system. Any parameter
with a cross (X) will return the value Zero (0000h). Some parameters are only available on the
Integra 1540, as shown in the table below..
Each parameter is held in the 3X registers. Modbus Function Code 04 is used to access all
parameters.
e.g. to request Volts 1 Start address = 00
No of registers = 02
Volts 2 Start address = 02
No of registers = 02
Each request for data must be restricted to 40 parameters or less. Exceeding the 40 parameter
limit will cause a Modbus exception code to be returned.