Setting The Address Areas And Accessing The As-I User Data - Siemens SIMATIC C7-621 Manual

Programming Preparations

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
256 reserved
257 Slave 2
258 Slave 4
259 Slave 6
260 Slave 8
261 Slave 10
262 Slave 12
263 Slave 14
Bit 3 I Bit 2 I Bit 1 i Bit 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.
Cycle
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.
18
Bit 3-0
Slave 1
Slave 3
Slave 5
Slave 7
Slave 9
Slave 11
Slave 13
Slave 15
Bit 3 I Bit 2 I Bit 1 i Bit 0
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.
I/O byte number Bit 7-4
264 Slave 16
265 Slave 18
266 Slave 20
267 Slave 22
268 Slave 24
269 Slave 26
270 Slave 28
271 Slave 30
Bit 3 I Bit 2 I Bit 1 i Bit 0
Start of program
End of program
Bit 3-0
Slave 17
Slave 19
Slave 21
Slave 23
Slave 25
Slave 27
Slave 29
Slave 31
Bit 3 I Bit 2 I Bit 1 IBit 0
Program
Getting Started with C7-621-AS-i
04/99