Quatech INTERBUS S manual Structure of Input and Output data, T Dmax=

(100D)

Structure of Input and Output data

The input data contain the CLOCK frequency as a binary value. The representation depends on the RANGE_SEL bits in the CONTROL byte. Even the method of measuring is selected via these bits. The following table illustrates the different modes.

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Attention:

When a new frequency range is requested, the application has to wait for valid data until the RANGE_SEL ACK bits contain the new frequency range. The maximum delay can be calculated using the following formula

TDmax= 2 *	number of periods to be integrated
	actual frequency

If the gate is enabled the input data contains the last valid frequency value. In this state the application cannot request a new range.

The valid frequency range stretches from 0.1 Hzup to 10 kHz (100000D).

To recognize static CLOCK signals, a watchdog timer is implemented. The default value for the timer is 10s. The timer resets on every Power On.

The application is able to change the watchdog time during operation by using the CONTROL byte.

This can be initiated by writing the corresponding value into the output bytes OUTPUT_DATA 1 and OUTPUT_DATA 0 before setting the TVD REQ bit in the CONTROL byte.

The success of the parameter transfer is acknowledged by the module via the TVD ACK bit in the STATUS information.

Attention:

The range of the watchdog timer stretches from 0 to 16383ms (0x0000H to 0x3FFFH) in steps of 1ms per digit.

Values which raise the permitted range of the watchdog timer are masked with 0x3FFF. If the maximum possible frequency of the different ranges is raised (see the table with maximum frequency ratings), the module will return the non valid data 0xFFFFFFFFH.

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