Pepper Computer RS485 User Manual

SMART I/O User’s Manual

©1996 PEP Modular Computers GmbH

March 12, 1996

Page 2 - 35

Chapter 2  SMART-BASE

: This call starts the counter; it’s syntax is as follows :

<RetVar> := OPERATE(<iovar>, O_START_COUNTER, <null>);

  where the 

<iovar>

 is typically t_in.

: With this call the contents of the counter register

  may be read. When this call is issued, the counter is

  stopped, it’s register read and then restarted. If a

  high-frequency input exists then pulses may be lost

  (not counted). The same effect may also be true due

  to timeslicing during timer stop and start operations.

  Therefore it is recommended that this call be only

  used for low frequency inputs (<1kHz). There is no

  detection for counter overflow and the call should

  not be used for count down operations or square

  wave generation. It’s syntax is as follows :

<RetVar> := OPERATE(<iovar>, O_READ_COUNTER, <null>);

  where the 

<iovar>

 is typically t_in.

: This call stops the counter counting up or down and

  square-wave generation and has the following

  syntax :

<RetVar> := OPERATE(<iovar>, O_STOP_COUNTER, <null>);

  where the 

<iovar>

 is typically t_in.

The counter/timer is configured automatically as MODE10 (refer to the ‘C’

Programming section) and from within ISaGRAF there is no ability to alter

this configuration.