Analog Input/Output Modules

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.

Time-Controlled

Another method is that of time-controlled program processing. With this

Program

method, certain program segments (e.g. FB 13) are automatically inserted

Processing

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

LEN=22

ABS

 

 

 

 

 

SHEET 1

 

SEGMENT 1

 

 

 

 

 

NAME: SELSAMPL

 

EXAMPLE OF SELECTIVE SAMPLING

 

0005

:

 

 

 

 

0006

:

 

 

 

 

0007

:L

PW128

READ ANALOG VALUE

 

 

0008

:T

FW128

IN TO AUX: FLAG 128

 

 

0009

:S

F 129.2

SCAN ACTIVITY=1?

 

 

000A

:JC

= END

IF = 1, JUMP TO END

 

 

000B

:T

FW10

IF = 0, MEASURED VALUE IN FW 10

 

000C

:T

PB128

INITIATE SAMPLING

 

 

000D END

:

 

(1ST VALUE INVALID AFTER START)

 

000E

 

 

 

 

 

000F

:

 

 

 

 

0010

:BE

 

 

 

Function Block You can read analog values of analog input modules with a function block from the ªbasic functionsº package.

BASP (Output

The BASP signal is not interpreted by the 460 analog input module.

Inhibit)

 

System Manual

9-55

C79000-G8576-C199-06

Page 437
Image 437
Siemens S5-135U/155U appendix To AUX Flag