3-5
3 Data Exchange with the CPU Unit
CJ-series PROFIBUS Slave Unit Operation Manual for NJ-series CPU Unit (W510)
3-3 I/O Dat
a F
o
rmat
3
3-3
I/O Data Format
The CJ1W-PRT21 allows the user to select between two methods to map the word-oriented CPU data
to the essentially byte-oriented PROFIBUS-DP messages. The default method is Motorola format (Big-
Endian), which allows easy data exchange with other OMRON PROFIBUS-DP devices. For communi-
cation with other manufacturers’ devices, in some cases it may be more convenient to select Intel for-
mat (Little-Endian).
Motorola (Big-Endian)
By default, the most significant byte of a CPU data word will be mapped to an even byte in the PRO-
FIBUS-DP message, the least significant byte is mapped to an odd byte, e.g.
Intel (Little-Endian)
Alternatively, selecting Intel format will result in:
Additional Information
Variable
*_SlavOutEndianMdSta
indicates how the data bytes of a PROFIBUS data telegram are
mapped to Host CPU data words (see section
3-7-2 Slave Output Data (*_SlvOutSta)
)
•
0: Motorola (high byte first),
•
1: Intel (low byte first).
CPU Data Area
PROFIBUS-DP Message
Bit #
Bit #
Word
15 to 8
7 to 0
7 to 0
Byte
8 9
0
0
8 9
A B
A B
1
C D
2
1
C D
E F
E F
3
CPU Data Area
PROFIBUS-DP Message
Bit #
Bit #
Word
15 to 8
7 to 0
7 to 0
Byte
0
8 9
A B
A B
0
8 9
1
1
C D
E F
E F
2
C D
3
