Intelligent Technologies Modbus to QCPort Adapter Manual
January 2006
MN05002002E (C)
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Page 31
Floating Point Mapping
Floating point data formats are 32 bit quantities; consequently, floating point numbers are
stored in two consecutive registers.
Table 27. IEEE-754 Floating Point Format
Bit 31
Bits 30..23
Bits 22………………0
Sign Exponent
Fractional
Portion
The IEEE-754 Floating Point Single Precision Standard is used to format QCPort 24 bit
floating point numbers for use on the Modbus network. Due to the Big endian
requirements of Modbus, multi-register floating point data will be formatted as shown in
Table 28.
Table 28. Modbus Floating Point Format
Bits 15…..8
Bits 7…..0
Bits 31…..24
Bits 23…..16
1
st
Byte
0
th
byte
3
rd
byte
2
nd
byte
Connection Timeout
A Connection Timeout register guards against loss of communication to the Modbus
Adapter. Every time a valid message is sent to the consumption data area (registers
1025 – 2048), the timer is reset and starts timing again. When the timer expires, the
scan for Channel A and Channel B will be disabled allowing the QCPort devices to enter
their communication loss action. This is a safety feature that can be disabled (default) or
set to 200ms increments.
Notice
The Modbus Adapter will round up to the nearest 200ms if a value is chosen that is not
a multiple of 200.
Once this timer expires, the scan registers 2049 and 2050 or 1025 will need to be set to
re-enable scanning.
Description Modbus
Register
Size
(Reg)
Usage Read/
Write
Connection Timeout 7526
1
milli-second connection timeout. 0 =
disabled, increments of 200ms
(automatically rounds up to the
nearest 200ms)
R/W