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Appendix B: Profibus
™
DP Slave Communication
70 312785C
How Addressing Works
PLC addressing is in byte and uses the scheme shown
in F
IG. 66.
The Gateway addressing follows a different scheme, as
shown in F
IG. 67.
This means that the address number will be different
when accessing words or Dwords in the Gateway data
tags than the PLC. Table 6 shows the address relation-
ship for integer tags mapped as word in the Gateway.
F
IG. 66. PLC Addressing Scheme
Byte 0
Byte 1
Byte 2
Byte 3
Byte 4
Byte 5
Byte 6
Byte 7
Byte 8
Byte 9
Word 0
Word 2
Word 4
Word 6
Word 8
Dword 0
Dword 4
Note how a Dword or word address starts at the
address of the first byte included in it.
F
IG. 67. Gateway Addressing Scheme
Byte 0
Byte 1
Byte 2
Byte 3
Byte 4
Byte 5
Byte 6
Byte 7
Byte 8
Byte 9
Word 0
Word 1
Word 2
Word 3
Word 4
Dword 0
Dword 1
Here, the word or Dword addresses follow the nor-
mal numeric increment and are not directly related
to the word or bytes they are composed of.
Table 6: Addressing Relationship
Block Type
PLC Gateway
Input (bytes) Output (bytes) Input (words) Output (words)
64 words in, 64 words out 256...383 256...383 0...63 0...63
16 words in 384...415 - 64...79 -
5 words out - 384...393 - 64...68