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5 Operation
CJ-series PROFINET IO Controller Unit Operation Manual for NJ-series CPU Unit (W511)
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nd Conversion
The following format conversions are required:
•
A sequence of 8-bit bytes, either signed or unsigned must be mapped to the CPU data area
words on a low-byte/high-byte sequence. If the number of bytes is even, all bytes will fit in the
words. If the number of bytes is odd, the last byte of the sequence will be mapped to the low-
byte of the last word. The high-byte of the last word must be padded with a 0.
•
A 16-bit word or a sequence thereof, either signed or unsigned must be mapped to the CPU
data area words on a high-byte/low-byte sequence.
•
A 32-bit double word or a sequence thereof, either signed or unsigned must be mapped to the
CPU data area words on a high-byte/low-byte sequence as well as on a high-word/low-word
sequence.
All conversions work both ways, i.e. when transferring data from the CPU data area to the PROFI-
NET IO network and when transferring data from the PROFINET IO network to the CPU data area.
The following conversion steps are required here: Every two data bytes are stored in 1 word in the
same sequence as in the case of 16-bit integer data, but the two words, required to store the 4 bytes
must be swapped, for the CPU data area. The conversion has to be reversed when transferring data
from the CPU data area to the PROFINET network.
Text Strings
Both PROFINET IO and the CJ1 System define the ASCII text strings as data format. The figure
below shows the format both on the PROFINET IO network and in the CPU data area. The data
bytes on the PROFINET IO network are transmitted in the sequence shown in the figure, i.e. Byte 0
is transmitted and received first, after that byte 1, etc.
