Siemens SIMATIC ET 200S Operating Instructions Manual page 148

1Count5V
3.6 Count Modes
Counter Status ≤ Comparison Value and Counter Status ≥ Comparison Value
If the comparison conditions are fulfilled, the respective comparator switches on the output.
The status of the output is indicated by STS_DO1 and STS_DO2.
The control bits CTRL_DO1 or CTRL_DO2 must be set for this.
The comparison result is indicated by the status bits STS_CMP1 or STS_CMP2. You cannot
acknowledge and thus reset these bits until the comparison conditions are no longer fulfilled.
Isochronous mode: In isochronous mode as well, the DO1 and DO2 outputs are switched as
soon as the comparison condition is fulfilled and are therefore independent of the bus cycle.
Comparison Value Reached, Output Pulse
If the counter status reaches the comparison value, the comparator switches on the
respective digital output for the assigned pulse duration.
The control bit CTRL_DO1 or CTRL_DO2 must be set for this.
The status bits STS_DO1 and STS_DO2 always have the status of the corresponding digital
output.
The comparison result is indicated by the status bit STS_CMP1 or STS_CMP2 and cannot
be reset by acknowledgment until the pulse duration has elapsed.
If a main count direction is assigned, the comparator switches only when the comparison
value in the main count direction is reached.
If a main count direction is not assigned, the comparator switches when the comparison
value is reached from either direction.
If the digital output is set by control bit SET_DO1 or SET_DO2, it is reset when the pulse
duration has elapsed.
Isochronous mode: In isochronous mode as well, the DO1 and DO2 outputs are switched as
soon as the comparison condition is fulfilled and are therefore independent of the bus cycle.
Pulse Duration when the Comparison Value is Reached
The pulse duration begins when the respective digital output is set. The inaccuracy of the
pulse duration is less than 2 ms.
The pulse duration can be set to suit the actuators used. The pulse duration specifies how
long the output is to be set for. The pulse duration can be preselected between 0 ms and
510 ms in increments of 2 ms.
If the pulse duration = 0, the output is set until the comparison condition is no longer fulfilled.
Note that the count pulse times must be greater than the minimum switching times of the
digital output.
Isochronous mode: In isochronous mode as well, the DO1 and DO2 outputs are switched as
soon as the comparison condition is fulfilled and are therefore independent of the bus cycle.
148
Technological Functions
Operating Instructions, 06/2010, A5E00124867-07