Siemens SIMATIC NET DP/AS-i Link 20E Manual page 56

Data exchange between DP master and AS-i slave
Table 2-4 Address area for the analog values of an AS-i slave
Byte no. (start address + offset)
Start address + 0
Start address + 1
Start address + 2
Start address + 3
Start address + 4
Start address + 5
Start address + 6
Start address + 7
A/B − Analog slaves occupy only a maximum of 2 channels. The A slaves, in this case, occupy bytes 0−3
and the B slaves bytes 4−7.
Notes on how to read the table 2-3 (examples):
1. Configuration: analog slaves have AS-i addresses 1−6
You use data record 140 and specify 48 as the data record length.
2. Configuration: 1 analog slave with AS-i address 7 is used
You use data record 141 and specify 24 as the data record length.
3. Configuration: the entire address area for 31 analog slaves is used
You use data record 140 and specify 224 as the data record length. This covers
analog slaves 1−28.
For the other analog slaves 29−31, you use record 147 in a second job and
specify 24 as the record length.
4. Configuration: analog slaves are located in the address area 29−31
You use data record 147 and specify 24 as the data record length.
Representation of the analog values
The analog values are interpreted as 16-bit values in two's complement.
The transparent values are interpreted as two independent bytes.
For further information regarding the range of values, the measurement range and
the accuracy please refer to the relevant documentation of the analog slaves.
Special situations in analog value transfer in the output direction
S With firmware version V2.x, the AS-i master interrupts the transfer of the analog
output values when the CPU is in STOP. How the analog slave reacts depends
on the particular device.
S As of firmware V3.0, the AS-i master sends the substitute value "0" to all slaves
when the CPU is in STOP.
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Analog value channel
Channel 1 / high byte
Channel 1 / low byte
Channel 2 / high byte
Channel 2 / low byte
Channel 3 / high byte
Channel 3 / low byte
Channel 4 / high byte
Channel 4 / low byte
DP/AS-Interface Link 20E
Release 08/2008
C79000-G8976-C235−01