B–2 EPM 2200 POWER METER – INSTRUCTION MANUAL
DATA FORMATS APPENDIX B: MODBUS MAPPING FOR EPM 2200
B.3 Data Formats
ASCII: ASCII characters packed 2 per register in high, low order and without any
termination charcters.
Example: “EPM2200” would be 4 registers containing 0x5378, 0x6172, 0x6B31,
0x3030.
SINT16/UINT16:16-bit signed/unsigned integer.
SINT32/UINT32:32-bit signed/unsigned integer spanning 2 registers. The lower-addressed
register is the high order half.
FLOAT:32-bit IEEE floating point number spanning 2 registers. The lower-addressed
register is the high order half (i.e., contains the exponent).
B.4 Floating Point Values
Floating Point Values are represented in the following format:
The formula to interpret a Floating Point Value is: -1
sign
x 2
exponent-127
x 1.mantissa =
0x0C4E11DB9
-1
sign
x 2
137-127
x 1.11000010001110111001
-1 x 2
10
x 1.75871956
-1800.929
Formula Explanation
C4E11DB9 (hex) 11000100 11100001 00011101 10111001 (binary)
The sign of the Mantissa (and therefore the number) is 1, which represents a negative
value.
The Exponent is 10001001 (binary) or 137 decimal.
The Exponent is a value in excess of 127, so the Exponent value is 10.
Register 0 1
Byte0 101
Bit 7 6543210765432107654321076543210
Meaning s eeeeeeeemmmmmmmmmmmmmmmmmmmmmmm
sign exponent mantissa
Register 0x0C4E1 0x01DB9
Byte 0x0C4 0x0E1 0x01D 0x0B9
Bit 7 6543210765432107654321076543210
1 1000100111000010001110110111001
Meaning s eeeeeeeemmmmmmmmmmmmmmmmmmmmmmm
sign exponent mantissa
1 0x089 = 137 0b11000010001110110111001
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