Structure Of The Double Data Word In Fast Mode; Output Address Im Standard Mode; Reading Out Data Areas; Example Of Access To Encoder Values And Use Of The Freeze Function - Siemens SM 338 Reference Manual

Structure of the double data word in Fast Mode

For each encoder input the double data word is made up as follows:
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In the double data word of channel 0, the status of the I0 is set in bit 27 (status
digital input) and in the double data word of channel 1, the status of the digital input
I1 is set.
The bit is always = 0 in the double data word of channel 2.

Output Address im Standard Mode

7

Reading out data areas

You can read out the data areas in your user program with the STEP 7-Operation
L PED "xyz".

Example of access to encoder values and use of the freeze function

You want to read out and evaluate the value of the encoder at the encoder inputs.
The module start address is 256.
No output data are supported in fast mode.
Product Information on the Reference Manual Programmable Logic Controllers S7-300 Module Data Release 3
A5E00409892-01
27 24
25 bit sensor value in gray or binary code
Status digital input
1 = Group error (sensor error, ext. auxiliary voltage error)
1 = Parameter assignment error
1 = Ready for operation (checkback value valid)
0
Initial module address
Acknowledging the freeze function:
Bit 0 = encoder input 0
Bit 1 = encoder input 1
Bit 2 = encoder input 2
0
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