Data mode

MCE Data Types

There are 5 types of data that the MCE can return in data packets:

• sq1_fb: the feedback applied by the MCE to the 1^st stage SQUIDs:

<math>sq1\_fb_{t} = \frac{1}{2^{12}} \left[(gainp \times error_{t}) + (gaini \times \sum_{i=1}^{t} error_i) + (gaind \times [error_{t} - error_{t-1}]) \right]</math>

• error: the error calculated from the Series-Array signals sampled by the ADCs:

<math>error_{t+1} = \sum_{n=1}^{sample\_num} (adc\_reading_{n} - adc\_offset)</math>

• sq1_fb_filtered: the low-pass filtered SQ1 feedback (see 4-pole Butterworth low-pass filter ). The effective DC gain, including quantization error, is approximately 1218.

<math>filter_{t+1} = low\_pass\_filter(1218 \times sq1\_fb_{[t, t-1, t-2]})</math>

• num_flux_jumps: the value stored in the flux-jump counter. See Flux jumping .
• raw_data: raw 50 MHz data. See Raw Data .

Where <math>\sum_{i=1}^n error_i</math> is the integral of the error from the moment the pixel was locked, and

Where <math>\left[error_{n} - error_{n-1} \right]</math> is the difference between the current error value and the previous one.

Data Modes (current as of Readout Card firmware revision 4.0.c)

Data Mode	Summary	Pixel-Data Description	RC Firmware Revision
0	Error	32b (signed) co-added Error signal err[31:0]. error_mode0 = error	all
1	Feedback	32b (signed) SQ1 Feedback data fb[31:0]. When servo_mode = 3: feedback_mode1 = sq1_fb * 212	all
2	Filtered feedback	32b (signed) low-pass filtered SQ1 feedback data fb[31:0]. filtered_fb_mode2 = sq1_fb_filtered	2.0.5 and later
3	Raw 50 MHz	Raw 50 MHz ADC samples raw[13:i]. raw_mode3 = (adc_reading – adc_offset) / (2i), where i=0 in rev. 4.3.7 and i=6 in all previous firmware.	Only 3.0.6, 3.0.16, 3.0.25, 4.1.7, 4.2.7, 4.3.7
4	18:14 Mixed	Signed 18b SQ1 feedback fb[31] & fb[28:12] + signed 14b coadded error signal err[31] & err[12:0]. feedback_mode4 = sq1_fb error_mode4 = error	2.0.9 and later
5	24:8 mixed	Signed 24b SQ1 feedback fb[31:8] + signed 8b num_flux_jumps fj[7:0]. feedback_mode5 = sq1_fb * 24	all
6 obsolete	18:14 mixed	Signed 18b filtered data filter[31] & filter[27:11] + signed 14b coadded error signal err[31] & err[12:0]. filtered_fb_mode6 = sq1_fb_filtered / (211) error_mode6 = error	3.0.30 to 4.0.6 only
7	22:10 mixed	Signed 22b filtered data filter[31] & filter[27:7] + signed 10b coadded error signal err[31] & err[12:4]. filtered_fb_mode7 = sq1_fb_filtered / (27) error_mode7 = error / (24)	4.0.2 and later
8 obsolete	24:8 mixed	Signed 24b filtered data filter[31:8] + signed 8b num_flux_jumps fj[7:0]. filtered_fb_mode8 = sq1_fb_filtered / (28)	4.0.4 only
9	24:8 mixed	Signed 24b filtered data filter[31] & filter[23:1] + signed 8b num_flux_jumps fj[7:0]. filtered_fb_mode9 = sq1_fb_filtered/ (21)	4.0.5 and later
10	25:7 mixed	Signed 25b filtered data filter[27:3] + signed 7b num_flux_jumps fj[6:0]. filtered_fb_mode10 = sq1_fb_filtered / (23)	4.1.6, 4.0.b and later

Data Mode Notes

• Depending on the data mode, these values will be windowed in a different way. The notes in the table below explain the windowing, in terms of how many bits are reported and the relative scaling of the windowed value relative to some reference data mode.
• The 'data_mode' parameter of each readout card determines which signals end up in the frame data, and in what arrangement. In order to fit the desired data into 32 bits, a signal may be windowed (some upper and lower bits dropped) and put into some subset of the 32 bits. The table below explains the windowing and packing of the signals for all data modes of the MCE.
• The type, gain, and windowing of the data returned depends on what data mode the MCE is in. See the table at the bottom of this page for a complete listing of data modes.
• Generally, a data packet contains one data point per pixel, although there are exceptions to this:
  • Fast Data: packets contain data for a subset of pixels to allow readout at a faster rate: Fast Data Readout .
  • Raw Data: packets contain a 50MHz time stream of data starting from row zero.

Automatic loading of data with mas_data.pro

Please note that, by default, mas_data.pro will rescale data in the following way:

• error signals are rescaled to match the units of data mode 0.
• sq1 feedback is rescaled to sq1_feedback (DAC) units (i.e. data mode 1 divided by 2¹²)
• filtered sq1 feedback is rescaled to the units of data mode 2.

This means the IDL user does not need to worry about the windowing of the different data modes for many applications.