－23－
5.5.9 Read floating data
[Function code: 70 (46H)]
A specified number of "floating data (floating-point data)" is read out of the designated numbers. This
function code is not available in the standard MODBUS. 4 bytes of data (32 bits) constitute one floating
data.
The format of floating data conforms to IEEE754.
S E
M
31 30
23 22
0
S: Code bit of fixed-point part
E: Characteristic part (8 bits)
M: Fixed-point part (23 bits)
Value = (-1)
S
×
1. M
×
2
E-127
Example) Reading floating data of CH No.1 and CH No.2 of the slave unit 1.
(Read 2 Reference Nos. from 50101 to 50102 of floating data for the slave unit 1)
Address 50101
50102
Data
1234.5
(44H,9AH,50H,00H)
1.2345
(3FH,9FH,6FH,D2H)
（
RTU data
）
Master
→
Instruments
Master
→
PC
(normal)
Slave address
01H
Slave address
01H
Function code
46H
Function code
46H
Number of data
00H
Number of data
00H
Start No. (H)
00H
Number of data
08H
Start No. (L)
64H
1st data (1)
00H
Number of Reference
No. (H)
00H
1st data (2)
50H
Number of Reference
No. (L)
02H
1st data (3)
9AH
CRC (L)
C5H
1st data (4)
44H
CRC (H)
78H
Next data (1)
D2H
Next data (2)
6FH
Next data (3)
9FH
Next data (4)
3FH
CRC (L)
28H
CRC (H)
3DH
LRC
53H
LRC 64H
Note) Data type is fixed at 00H.
Note) Start No. (Relative No.) is given by "Reference No. - 50001". (Decimal number 100 (=50101 - 50001)
Hexadecimal 64H)
Note) No. of data is the number of data bytes.
(which is different from the requested number of data. In the example given above, the requested
number of Reference No. is 2 and the number of data is 8).
Note) The floating-point data is transmitted from LSB.
(Error check in ASCII mode)
