Accessing The As-I User Data (Bm141, Bm142) - Siemens SIMATIC NET CP 142-2 Manual

B8976111/02
Figure 3-1 shows an example of how a slave is addressed by a user program with start addresses m
= 256 for the input data and n = 256 for the output data. The bits relevant for the user program are
shown on a gray background. The bits on a white background are irrelevant for the user program.
Inp ut
b yte
reserved
256
Slave 2
257
B it 3
Bit 2 Bit 1 Bit 0
Slave 4
258
Bit 3 Bit 2 Bit 1 Bit 0
.
.
.
Slave 30
B it 3
2 7 1 Bit 2 Bit 1 Bit 0
7 6 5 4
Slave No. 2
4I module
Figure 3-1 Mapping the Slave Addresses on the I/O Addresses
In the diagram above, the 2I/2O module (two inputs and two outputs) occupies bits 0 and 1 in input
byte 257 and bits 2 and 3 in output byte 257. The assignment of the AS-i connections of the bus
modules to the data bits of the input/output bytes is shown below taking slave no. 3 as an example:
Input byte 257
module
Output byte 257

3.2.2 Accessing the AS-i User Data (BM141, BM142)

Access to the AS-i user data depends on the PROFIBUS master you are using. For further
information, refer to /4/.
Slave 1
Bit 3 Bit 2 Bit 1 Bit 0
Slave 3
Bit 3 Bit 2 Bit 1 Bit 0
Slave 5
Bit 3 Bit 2 Bit 1 Bit 0
Slave Slave 31
Bit 3 Bit 2 Bit 1 Bit 0
31
Bit 3 Bit 2 Bit 1 Bit 0
3 2 1 0
AS -i slaves
Slave No. 3
2I/2O module
O utput
byte
256 reserved
Slave 2
257
B it 1
Bit 3 Bit 2
Slave 4
258
Bit 3 Bit 2 Bit 1
.
.
.
Slave 30
B it 1
2 71 Bit 3 Bit 2
7 6 5
Slave No. 4 Slave No.31
4O module 4I/4O module
1 0
Connector 1 on the AS-i bus
Connector 2 on the AS-i bus module
3 2
Connector 3 on the AS-i bus module
Connector 4 on the AS-i bus module
3-4
AS-i Master Module CP 142-2
Slave 1
B it 3 B it 2 Bit 1 Bit 0
Slave 3
B it 3 B it 2 Bit 1 Bit 0
Bit 0
Slave 5
Bit 0 Bit 3 Bit 2 Bit 1 Bit 0
Slave Slave 31
Bit 3 31 Bit 2 Bit 1 Bit 0
Bit 0 Bit 3 Bit 2 Bit 1 Bit 0
4 3 2 1 0
Bit no.
Bit no.