WIKA D-21-9 - Manual (Page 5)

D-20-9 / D-21-9 GB
WIKA Additional Instructions Pressure Transmitter with CANopen Interface D-20-9 / D-21-9 5
1. Process Data Object (PDO)
ID DLC Byte0 Byte1 Byte2 Byte3
LSB MSB
ID 4
process value
The structure of the synchronous and asynchronous PDO is identical.
The identifier of the PDO can be set via object 1800h.
Factory-set: 180h + NID
Byte 0 to byte 3 contains the currently configured process value.
The default settings are configured to object 2090h subindex 0 (process value as integer).
The coding corresponds to DS301, chapter 9.1.4.5 “Signed Integer”
The user can switch the mapping to object 6130h subindex 1 (process value as float).
Then the coding corresponds to DS301, chapter 9.1.4.6 “Floating Point Numbers”
For further information about the data types see description below.
Data Types
Signed Integer
Byte0 Byte1 Byte2 Byte3
Integer32 b
7
..b
0
b
15
..b
8
b
23
..b
16
b
31
..b
24
The data is represented as bit sequence of length 32.
The bit sequence b = b
0
.. b
31
is assigned the value
INTEGER32(b) = b
30
*2
30
+ … + b
1
*2
1
+ b
0
*2
0
if b
31
=0
and, performing two’s complement arithmetic,
INTEGER32(b) = - INTEGER32(^b)-1 if b
31
=1
Floating Point Numbers
Byte0 Byte1 Byte2 Byte3
Real32 b
7
..b
0
b
15
..b
8
b
23
..b
16
b
31
..b
24
The data type REAL32 is represented as bit sequence of length 32.
The encoding of values follows the IEEE 754-1985 Standard for single precision floating-point.
The bit sequence b = b
0
.. b
31
is assigned the value
REAL32(b ) = (-1)
S
* 2
E-127
* (1+F)
Here
S = b
31
is the sign.
E = b
30
*2
7
+ …+ b
23
*2
0
; 0 < E < 255; is the un-biased exponent.
F = 2
-23
*(b
22
*2
22
+ …+ b
1
*2
1
+ b
0
*2
0
) is the fractional part of the number.