Pepper-computer Modular Computers RS485 Bedienungsanleitung PDF herunterladen (Seite 75)

SMART I/O User’s Manual

Chapter 2 SMART-BASE

O_START_COUNTER : 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.

O_READ_COUNTER : 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.

O_STOP_COUNTER : 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.

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Pepper-computer Modular Computers RS485 Bedienungsanleitung Seite 75