Spectrum Brands MC.31XX manual Option Timestamp, Timestamp modes, Limits, StartReset mode

Option Timestamp General information

Option Timestamp

General information

The timestamp function is used to record trigger events relative to the beginning of the measurement, relative to a fixed time-zero point or synchronized to an external radio clock. This is done by a wide resetable counter that is incremented with every sample rate. With every detected trigger event the actual counter value is stored in a seperate timestamp memory.

This function is designed as an enhancement to the Multiple Recording and the Gated Sampling mode but can also be used without these options. If Gated Sampling mode is used, then both the start and end of a recorded segment are timestamped.

The timestamp memory is designed as a FIFO buffer so that it can be read out even while the Spectrum board is recording data continuously to the PC in the FIFO mode. This extra memory is 64 K Timestamps in size.

Each recorded timestamp consists of the number of samples that has been counted since the last counter reset has been done. The actual time from the point since the last reset has been done so can easily be calculated by the formular besides.

If you want to know the time between two timestamps, you can simply calculate this by the for- mular besides.

Timestamp t = --------------------------------------------------

Sample rate

Timestampn + 1 – Timestampn ∆t = -----------------------------------------------------------------------------------------------------------------------------

Sample rate

Limits

The timestamp counter is running with the sampling clock on the base card. Some card types (like 2030 and 3025) use an interlace mode to double the sampling speed. In this case the timestamp counter is only running with the non-interlaced sampling rate. Therefore the maximum counting frequency of the timestamp option is limited to 125 MS/s.

Timestamp modes

Standard mode

In standard mode the timestamp counter is set to zero once by writing the TS_RESET commando to the com- mand register. After that command the counter counts continuously.

The timestamps of all recorded trigger events are refer- enced to this common zero time. With this mode you can calculate the exact time difference between differ- ent recordings.

The following table shows the valid values that can be written to the timestamp command register.

Register		Value	Direction	Description
SPC_TIMESTAMP_CMD		47000	w	Writes a command to the timestamp command register.
SPC_TIMESTAMP_CMD		47000	r	Reads out the actual timestamp mode.
	TS_RESET	0	Resets the counter of the timestamp module to zero.
	TS_MODE_DISABLE	10	Disables the timestamp module. No timestamps are recorded.
	TS_MODE_STANDARD	12	Must be written to enable the Standard timestamp mode. The counter must be manually reset by writing the command
			TS_RESET to the command register. The timestamps values will be relative to this reset time.

StartReset mode

In StartReset mode the timestamp counter is set to zero on every start of the board. After starting the board the counter counts continuously.

The timestamps of one recording are referenced to the start of the recording. This mode is very useful for Multi- ple Recording and Gated Sampling (see according chapters for detailed information on these two optional modes).

The following table shows the valid values that can be written to the timestamp command register.

Register		Value	Direction	Description
SPC_TIMESTAMP_CMD		47000	w	Writes a command to the timestamp command register.
SPC_TIMESTAMP_CMD		47000	r	Reads out the actual timestamp mode.
	TS_RESET	0	Resets the counter of the timestamp module to zero.
	TS_MODE_DISABLE	10	Disables the timestamp module. No timestamps are recorded.

(c) Spectrum GmbH 83