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4
Data flow
4.1
Transmission formats
4.1.1
Integer values
The "Big Endian" format (Motorola® format) is used to transfer integer values (also for the addresses):
The high byte first, followed by the low byte
Example: Request of the int value of Modbus address
(=
0x002D
Request:
0103000D000115C9
Response:
4.1.2
Floating-point values
In the case of Modbus float values, the IPC 300 operates with the IEEE-754 standard format (32 bits),
the only difference being that byte 1 and 2 are interchanged with byte 3 and 4.
SEEEEEE
Byte 1
S - Prefix sign bit
E - Exponent (two's complement)
M - 23-bit normalized mantissa
Modbus address x
MMMMMMM
Byte 3
Example: Request of the float value of Modbus address
(=
0x44098000 in IEEE-754 format
Request:
0103010400028436
Response:
Please find out the way float values are saved in your application. After being transmitted from the power
controller, the bytes for the float value may need to be interchanged accordingly.
4.1.3
Character strings (texts)
Character strings always finish with '\0' (ASCII code 0x00) as the end flag. Any characters after this mark
have no significance.
Example: Request of the text of Modbus address
0x43, 0x33, 0x30, 0x30, 0x20, 0x20, 0x00
Request:
0103000E0005E40A
Response:
(instead of 0x00 directly preceding CRC, any other value could also be stated)
The number of characters stated for strings in the following tables includes the final '\0'.
Example: "text (10 bytes)" means that the text is up to 9 characters long. The end flag '\0' is then added.
) is written beneath this address:
010302002D7859
EMMMMMMM
Byte 2
Modbus address x+1
MMMMMMM
SEEEEEE
Byte 4
Byte 1
0103048000440920F5
01030A495043333030202000000296
0x000D
MMMMMMM
MMMMMMM
Byte 3
Byte 4
EMMMMMMM
Byte 2
) is written beneath this address:
0x000E
) is written:
, if 45
Single-float format (32-bit)
according to standard IEEE
754
Modbus float format
, if 550.0
0x0104
to which "IPC300̺ " ̺ (ASCII code:
4 Data flow
0x49, 0x50,
15
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