Siemens S5-155U System Manual page 430

The 465 Analog Input Module
Time-controlled program
processing
Function block
BASP (output inhibit)
9 - 58
In the selective sampling mode, a measured value is encoded on the
central initiative of the CPU. At the start of conversion, the module
must be addressed once with a write operation (T PW) by the user
program. An active bit (T = 1) is set during encoding.
With the transition to T = 0, the measured value becomes valid. With
non-constant cycle times, there may be non-periodic measured value
aquisition. If you operate the module in this mode, you must set a
module address from 128 to 255. You can also use the address range
from 0 to 127 for selective sampling after appropriate programming in
DB 1 of the user program.
Another method is that of time-controlled program processing. With
this method, certain program segments (e.g. FB 13) are automatically
inserted into program processing at the 100 ms rate by a time-
controlled block (OB 13). A constant timebase is thus achieved.
FB 13 SPRM-B
SEGMENT 1
NAME: SELSAMPL
0005 :
0006 :
0007 :L PW 128
0008 :T FW 128
0009 :A F 129.2
000A :JC = END
000B :T FW 10
000C :T PB 128
000D END :
000E :
000F :
0010 :BE
You can read analog values of analog input modules with a function
block from the "basic functions" package.
The BASP signal is not interpreted by the 465 analog input module.
LEN=22 ABS
SHEET 1
EXAMPLE OF SELECTIVE SAMPLING
READ ANALOG VALUE
IN TO AUX: FLAG FW 128
SCAN ACTIVITY =1?
IF = 1, JUMP TO END
IF = 0, MEASURED VALUE IN FW 10
INITIATE SAMPLING
(1ST VALUE INVALID AFTER START)
System Manual
C79000-B8576-C109-03