Omron SYSMAC CJ1W-PRM21, Руководство по эксплуатации

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Appendix D
I/O Data Conversions
D-1 I/O Data type definitions
Standard PROFIBUS-DP defines two types of I/O data.
• 8-bit bytes sized data.
• 16-bit word sized data.
The standard for PROFIBUS extension, also referred to as PROFIBUS-DPV1, additional data types have been
defined:
• 8-bit byte signed / unsigned Integer data.
• 16-bit word signed / unsigned Integer data.
• 32-bit double word signed / unsigned Integer data.
• 32-bit single precision floating point (IEEE754 format)
• ASCII Text strings of undetermined length (in 8-bit bytes)
• 7 byte Date format
• 6 byte Time of Day format
• 6 byte Time Difference format
The CS1/CJ1-series PLC defines similar data types, which however differs in size and/or storage format in the
PLC Memory. Since the PROFIBUS-DP Master Units provides an interface between a PROFIBUS network and
the CS1/CJ1-series PLC, the Unit will provide the necessary conversions to ensure that the I/O data on the
PROFIBUS network is transferred to the PLC Memory in the correct format. This Appendix explains the conver-
sions in detail.
D-2 Integer Data Conversions
8-bit Byte Data
The CS1/CJ1-series PLC Memory layout is word oriented, and does not support storage of single 8-bit byte
type of data. The PROFIBUS-DP master will therefore convert a stream consisting of one or more bytes of data
in to words. The figure below shows the conversion in graphic format.
Note m = (n-1)/2, rounded to the next lowest integer.
A sequence of bytes transmitted over the PROFIBUS network is copied to the PLC Memory in the following
procedure.
PLC Data area
Byte
sequence
Byte 1
Byte 2
PROFIBUS
Bit 07 Bit 00
Byte n-1 Byte n Word m
Bit 15 Bit 00
Byte 1 Byte 2 Word 0
Byte n-1
Byte n