Basler DECS-200 User Manual

Modbus™ Communication DECS-200
7-8
Example:
The UI32 data type, value is 0xE0234567 and is mapped to two Holding registers (such as 45003 and
45004) as shown in Table 7-7.
Table 7-7. Typical Mapping
Register 45003 45004
Hexadecimal 4567 E023
Binary 0100 0101 0110 0111 1110 0000 0010 0011
HR 45002
LO byte
HR 45003
HO byte
HR 45003
LO byte
HR 45004
HO byte
HR 45004
LO byte
HR 45005
HO byte
... 45 67 E0 23 ...
Floating Point (R23_32) Data Format
The specific floating-point format matches the floating-point format used for Modicon 984-8 family of
programmable controllers.
Its representation in bit format is:
S EEE EEEE E MMM
MMMM
MMMM MMMM MMMM MMMM
byte 3 byte 2 byte 1 Byte 0
where the “S” is the sign bit for the floating point value: 1 if negative and 0 if positive; The “E” field is the
two’s complement exponent biased by 127 decimal; The “M” field is the 23-bit normalized mantissa. The
most-significant bit of the mantissa is always assumed to be 1 and is not explicitly stored yielding an
effective precision of 24 bits.
The value of the floating-point number is obtained by multiplying the binary mantissa times two raised to the
power of the unbiased exponent. The assumed bit of the binary mantissa has the value of 1.0 with the
remaining 23 bits providing a fractional value.
Table 7-8 shows the floating-point format.
Table 7-8. Floating Point Format
Sign 2's Complement Of (Exponent + 127) Mantissa
1 bit 8 bits 23 bits
The floating point format allows a maximum value of 3.38 x 10
38
.
Note that bytes 0 and 1 of the floating-point value are stored in the lower numbered register and bytes 2
and 3 are contained in the higher numbered register.
For example: Number 123 in floating point format is mapped to two Holding registers (such as 45005 and
45006) as shown in Table 7-9.
Table 7-9. Number 123 in Floating Point Format
Register 45005 45006
Hexadecimal 0000 42F6
Binary 0000 0000 0000 0000 0100 0010 1111 0110
CAUTION
For DECS-200 Modbus, two consecutive holding registers which are mapped to any of
the 4-byte generic data types, are considered to be linked together as one atomic,
indivisible unit of information which can be read or written by Modbus message only as
one entity (that is, one cannot be read or written without the other).

Basler DECS-200 Specifications

General

Brand	Basler
Model	DECS-200
Category	Controller
Language	English