Data mode

MCE Data Types

During data readout from the MCE, there are different types of data associated with each detector. These are:

1. calculated SQ1 feedback (sq1_fb):
   • <math>sq1\_fb_{n+1} = \frac{1}{2^{12}} \left[\left(gainp \times q_{n}\right) + \left(gaini \times \sum_{i=1}^{n} error_i\right) + \left(gaind \times [error_{n} - error_{n-1}]\right)\right] </math>
   • where <math> q_n=error_n + b\times q_{n-1}</math>
   • n is the multiplexing-frame index
   • i is reset when the PID servo is restarted by setting the servo_mode to 3 or flx_lp_init to 1.
   • b < 1 and specified by pterm_decay_bits. See mce_command_description.
2. coadded error (error):
   • calculated from the Series-Array signal sampled @ 50MHz by the ADC
   • <math>error = \sum_{1}^{sample\_num} (adc\_reading_{i} - adc\_offset)</math>
3. low-pass filtered SQ1 feedback (sq1_fb_filtered):
   • see 4-pole Butterworth low-pass filter .
   • The effective DC gain, including quantization error, is approximately: <math>sq1\_fb\_filtered_{n} \simeq 1218 \times \left[sq1\_fb_{n-1}\right]</math>
4. flux-jump counter (num_flux_jumps). See Flux jumping .
5. raw ADC samples @ 50 MHz (raw). See Raw-mode readout .

Note that error, sq1_fb, and sq1_fb_filtered are internally stored as 32 bits while num_flux_jumps are stored as 8 bits and raw as 14 bits. During readout the appropriate windowing is chosen for each data type.

Data Modes and Windowing

The type of data reported by the MCE during data acquisition is determined by the MCE parameter data_mode. Depending on the data mode, the reported data 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 reference data modes for error, sq1fb and filtered_sq1fb are, respectively, 0, 1, and 2.

data-mode	data-type	Description	RC Firmware Revision
0	error	32b (signed) co-added error [31:0] = error	all
1	sq1_fb	32b (signed) calculated SQ1 feedback. [31:0] = sq1_fb * 212 when servo_mode =3 [31:0] = sq1_fb when servo_mode != 3 Note that servo_mode=3 is the normal running condition. The non-servoing form, used at times during array-auto-tune for example, is included here for completeness.	all
2	filtered_sq1_fb	32b (signed) low-pass filtered SQ1 feedback data. [31:0] = sq1_fb_filtered	2.0.5 and later
3 obsolete (see 12)	raw	Raw 50 MHz ADC samples raw[13:i], where i=0 in rev. 4.3.7 and i=6 in all previous firmware. [31:0] = raw_data / (2i),	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 + signed 14b coadded error [31:14] = sq1_fb [13:0] = error	2.0.9 and later
5	24:8 mixed	signed 24b SQ1 feedback + signed 8b num_flux_jumps[7:0]. [31:8] = sq1_fb * 24 [7:0] = num_flux_jumps	all
6 obsolete	18:14 mixed	signed 18b filtered data + signed 14b coadded [31:13] = sq1_fb_filtered / (211) [12:0] = error	3.0.30 to 4.0.6 only
7	22:10 mixed	signed 22b filtered data + signed 10b coadded error [31:10] = sq1_fb_filtered / (27) [9:0] = error / (24)	4.0.2 and later
8 obsolete	24:8 mixed	signed 24b filtered data + signed 8b num_flux_jumps[7:0]. [31:8] = sq1_fb_filtered / (28) [7:0] = num_flux_jumps	4.0.4 only
9 obsolete	24:8 mixed	signed 24b filtered data + signed 8b num_flux_jumps[7:0]. [31:8] = sq1_fb_filtered/ (21) [7:0] = num_flux_jumps	4.0.5 till 4.0.a
10	25:7 mixed	Signed 25b filtered data + signed 7b num_flux_jumps. [31:7] = sq1_fb_filtered / (23) [6:0] = num_flux_jumps	4.1.6, 4.0.b and later
11	6:3 mixed, debugging mode	Unsigned 6b row_index + unsigned 3b column_index. [31:10] ---- [9:3] row_index [2:0] column_index	5.0.0 and later
12	raw	Raw 50 MHz ADC samples raw[13:0], sign-extended to 32 bits. [31:0] = raw_data	4.0.d, 4.0.e, 5.0.1+

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.

Links

• MCE firmware
• Main Page