4
Data Exchange between User Program and AS−i Slaves
40
CP 343−2 / CP 343−2 P AS−Interface Master
Release 08/2008
C79000−G8976−C149−04
4.1.1
Addressing the Standard or A Slaves with the PLC
Each standard or A slave on the AS-i cable is assigned four bits (a nibble) by the
CP 343-2. The PLC can write (slave output data) and read (slave input data) this
nibble. This allows bi-directional slaves to be accessed.
The first four input bits (first nibble) are reserved for using FC “ASI_3422”. If you
do not use an FC, the first four input bits alternate between the values 8H and EH
approximately every 2.5 seconds. The first four output bits (first nibble) have no
significance for the CP 343-2.
Assignment:
I/O byte number
Bit 7−4
Bit 3−0
n+0
reserved
Slave 1 or 1A
Bit 3 | Bit 2 | Bit 1 | Bit 0
n+1
Slave 2 or 2A
Slave 3 or 3A
n+2
Slave 4 or 4A
Slave 5 or 5A
n+3
Slave 6 or 6A
Slave 7 or 7A
n+4
Slave 8 or 8A
Slave 9 or 9A
n+5
Slave 10 or 10A
Slave 11 or 11A
n+6
Slave 12 or 12A
Slave 13 or 13A
n+7
Slave 14 or 14A
Slave 15 or 15A
n+8
Slave 16 or 16A
Slave 17 or 17A
n+9
Slave 18 or 18A
Slave 19 or 19A
n+10
Slave 20 or 20A
Slave 21 or 21A
n+11
Slave 22 or 22A
Slave 23 or 23A
n+12
Slave 24 or 24A
Slave 25 or 25A
n+13
Slave 26 or 26A
Slave 27 or 27A
n+14
Slave 28 or 28A
Slave 29 or 29A
n+15
Slave 30 or 30A
Bit 3 | Bit 2 | Bit 1 | Bit 0
Slave 31 or 31A
Bit 3 | Bit 2 | Bit 1 | Bit 0
n = base address
The table shows the assignment of the CP 343-2 interface for standard and A
slaves (where n is the base address of the I/O address area occupied by the
CP 343-2). The assignment of the slave I/O bits to the I/O byte of the PLC can
also be seen in the table.
Special Feature of AS-i Analog Slaves
If you use AS-i analog slaves complying with profile 7.3 /7.4, the following applies:
S
The input nibbles of these AS-i slaves are set to the value “0” by the CP 343-2;
S
The output nibbles of these AS-i slaves are ignored by the CP 343-2;
