Siemens CP 243-2 Manual Do Utilizador

Access to the Data of the AS-i Slaves

3-6

SIMATIC NET CP 243-2 AS-i Master

C79000-G8976-C142/02

Example

Figure 3-1 shows an example of the CP 243-2 addressing four AS-i slaves. In the
example, m = 0 is the start address for the input data and n = 0 is the start address
for the output data.

The bits relevant for the user program (existing AS-i slaves) are shown on a gray
background. The bits on a white background are irrelevant for the user program.

CP 243-2

16 input bytes

.
.
.

4 I module

Slave no. 2

Slave no. 3

Slave no. 4

Slave no. 31

AS-i slaves

4 I module

4 I/4 O module

2 I/2 O module

4 O module

Slave 1

Slave 2

Slave 3

Slave 30

Slave 31

Slave 4

Slave 5

Slave 2

Slave 3

Slave 4

Slave 5

Slave 30

Slave 31

Bit 0

Bit 1

Bit 2

Bit 3

Bit 0

Bit 1

Bit 3

Bit 2

Bit 3

Bit 2

Bit 3

Bit 1 Bit 0

output bytes

Figure 3-1

In the figure above, for example, the 2I/2O module (AS-i slave number 3 with two
inputs and two outputs) occupies bits 0 and 1 in input byte 1 and bits 2 and 3 in
output byte 1.

The assignment of the AS-i terminals of the bus modules to the data bits of the
input/output bytes is shown below based on the example of slave number 3:

Bit no.

Input byte 1

Terminal 1 on the AS-i bus module

Terminal 2 on the AS-i bus module

Bit no.

Output byte 1

Terminal 3 on the AS-i bus module

Terminal 4 on the AS-i bus module