Siemens SIMATIC NET CP 142-2, Manual, Page: 24 / 84

B8976111/02 AS-i Master Module CP 142-2
3-2
3.2 How the User Program Addresses the AS-i Slaves
3.2.1 Addressing AS-i User Data
Each slave on the AS-i cable is assigned four bits (a nibble) of input data and four bits of output data
by the CP 142-2. This nibble can be written (slave output data) and read (slave input data). This
allows bi-directional slaves to be accessed.
In total, the maximum of 31 AS-i slaves occupy 16 bytes of input data and 16 bytes of output data
(see table below).
±
When using the CP with the BM141/BM142, the start addresses m and n of the input or output
data depend on the configuration of the PROFIBUS DP master.
±
When using the CP with the BM147, the start addresses depend on the slot of the CP (see
Section 3.1.2). The values m and n are then always the same.
Assignment of the input data of the slaves
Byte Number Bits 7-4 Bits 3-0
m+0 Reserved for FC “ASI_3422” Slave 1
Bit 3 | Bit 2 | Bit 1 | Bit 0
m+1 Slave 2 Slave 3
m+2 Slave 4 Slave 5
m+3 Slave 6 Slave 7
m+4 Slave 8 Slave 9
m+5 Slave 10 Slave 11
m+6 Slave 12 Slave 13
m+7 Slave 14 Slave 15
m+8 Slave 16 Slave 17
m+9 Slave 18 Slave 19
m+10 Slave 20 Slave 21
m+11 Slave 22 Slave 23
m+12 Slave 24 Slave 25
m+13 Slave 26 Slave 27
m+14 Slave 28 Slave 29
m+15 Slave 30
Bit 3 | Bit 2 | Bit 1 | Bit 0
Slave 31
Bit 3 | Bit 2 | Bit 1 | Bit 0
m = start address of the input data