9 Communication
9.2 Modbus
156
SICAM MMU 7KG9663, Device Manual
E50417-H1040-C514-A3, Edition 01.2016
Accuracy of the Floating-point Numbers
The 32-bit floating-point numbers have a 23-bit mantissa. Integer numbers can be represented in the following
ranges without loss of accuracy:
•
Binary:±(1)111 1111 1111 1111 1111 1111
•
Hexadecimal:±FF FF FF
•
Decimal:±16777216
32-bit floating-point numbers are accurate to about 7 decimal digits. An accuracy of 4 decimal digits (0.2 mea-
suring error) is required for measuring alternating-current quantities.
9.2.6.2
Data Type - Date/Time
The
Date/Time
data type is used to transmit the local time. The following format is used:
Date/time Status
10H set: Daylight saving time active
20H set: Date/time error (equivalent to FAIL bit in Table 8-1).
Byte 1 (MSB)
Holding register 0065
Byte 0 (LSB)
Milliseconds (0 to 59 999)
...
...
Byte 3
Holding register 0066
Byte 2
Hours (0 to 23)
Minutes (0 to 59)
Byte 5
Holding register 0067
Byte 4
Month (1 = Jan. to 12 = Dec.)
Day (1 to 31)
Byte 7
Holding register 0068
Byte 6
Date/time status
Year (0 = 1900)
NOTE
For the time synchronization via Ethernet, Siemens recommends the use of NTP, see chapter 8.
SICAM-MMU_7KG9663_US.book Page 156 Monday, December 7, 2015 12:22 PM