Siemens simatic c7-621, Руководство пользователя

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Programming Preparations 04/99
18 Getting Started with C7-621-AS-i
Setting the address areas and accessing the AS-i user data
In standard operation, the AS-i communications processor behaves like an I/O module. It occupies
16 input and 16 output bytes in the analog area of the controller. Each slave on the AS-i cable is assigned
four bits (a nibble) by the C7-AS-i-CP. The C7-CPU can access a nibble for reading and writing. The start
address of this address area is fixed at 256 in the C7-AS-i. For the assignment of the slave I/O bits to the
I/O bytes of the C7-CPU, see the AS-i interface table.
Assignment table
I/O-byte number Bit 7-4 Bit 3-0 I/O byte number Bit 7-4 Bit 3-0
256 reserved Slave 1 264 Slave 16 Slave 17
257 Slave 2 Slave 3 265 Slave 18 Slave 19
258 Slave 4 Slave 5 266 Slave 20 Slave 21
259 Slave 6 Slave 7 267 Slave 22 Slave 23
260 Slave 8 Slave 9 268 Slave 24 Slave 25
261 Slave 10 Slave 11 269 Slave 26 Slave 27
262 Slave 12 Slave 13 270 Slave 28 Slave 29
263 Slave 14 Slave 15 271 Slave 30 Slave 31
Bit 3 I Bit 2 I Bit 1 i Bit 0 Bit 3 I Bit 2 I Bit 1 i Bit 0 Bit 3 I Bit 2 I Bit 1 i Bit 0 Bit 3 I Bit 2 I Bit 1 IBit 0
The parameters required in the application appear on a gray background.
The diagram below illustrates the access to the input and output data of the individual slaves.
Because the bits of the AS-i line can only be accessed in word mode or doubleword mode, it is necessary
to set up a memory data block. In the data block the AS-i data can be accessed in bit mode.
Transfer the image of the AS-i
input data to a data block.
Evaluate individual bits and
perform, e.g., logic operations,
setting and resetting, arithmetic
operations and counting.
Copy the output data of the data
block to the AS-i output data.
Cycle
Start of program
Program
End of program