Data mode

In MCE-speak, a "data mode" or "data_mode" is a way of encoding MCE signals into binary data. Data modes are readout parameters, and do not affect the way that the MCE servos, multiplexes, biases, or phi0-corrects.

MCE Data Types

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

1. sq1_fb: the feedback applied by the MCE to the 1^st stage SQUIDs:
   • <math>sq1\_fb_{n+1} = \frac{1}{2^{12}} \left[\left(gainp \times error_{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>\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.
   • Where 'n' is the frame period index
   • Where 'i' is the frame period index since the PID-loop was locked (servo_mode = 3)
2. error: the error calculated from the Series-Array signals sampled by the ADCs:
   • <math>error = \sum_{i=1}^{sample\_num} (adc\_reading_{i} - adc\_offset)</math>
3. 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:
   • <math>sq1\_fb\_filtered_{n} \simeq 1218 \times \left[sq1\_fb_{n-1}\right]</math>
4. num_flux_jumps: the value stored in the flux-jump counter. See Flux jumping .
   • <math>num\_flux\_jumps_{n} = \frac{1}{flux\_quanta} \left[(sq1\_fb_{n}) - (sq1\_fb\_applied\_to\_DAC_{n})\right] </math>
5. raw_data: raw data sampled @ 50 MHz. See Raw-mode readout .
   • <math>raw\_data = \left[adc\_reading\right]</math>
   • NOT <math>raw\_data = \left[adc\_reading - adc\_offset\right]</math>

Data Modes and Windowing

• The data modes below offer the types of data listed above in various combinations, and with different windowings. Each data point in a data packet is 32 bits wide, and may have several types of data packed into it. The table below specifies the different packings.
• The table below makes liberal use of variables sq1_fb, error, sq1_fb_filtered, num_flux_jumps, and raw_data, which are defined above.
• 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: High rate acquisition .
  • Raw Data: packets contain a 50MHz time stream of data starting from row zero.

Data Mode	Summary	Pixel-Data Description	RC Firmware Revision
0	Error	32b (signed) co-added Error signal err[31:0]. [31:0] = error	all
1	Feedback	When servo_mode = 3: 32b (signed) SQ1 Feedback data fb[31:0]. [31:0] = sq1_fb * 212 When servo_mode != 3: 32b (signed) SQ1 Feedback from the rc? fb_const registers. These are DAC values. [31:0] = sq1_fb 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 feedback	32b (signed) low-pass filtered SQ1 feedback data fb[31:0]. [31:0] = sq1_fb_filtered	2.0.5 and later
3 obsolete (see 12)	Raw 50 MHz	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 fb[31] & fb[28:12] + signed 14b coadded error signal err[31] & err[12:0]. [31:14] = sq1_fb [13:0] = 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]. [31:8] = sq1_fb * 24 [7:0] = num_flux_jumps	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]. [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 filter[31] & filter[27:7] + signed 10b coadded error signal err[31] & err[12:4]. [31:10] = sq1_fb_filtered / (27) [9:0] = 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]. [31:8] = sq1_fb_filtered / (28) [7:0] = num_flux_jumps	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]. [31:8] = sq1_fb_filtered/ (21) [7:0] = num_flux_jumps	4.0.5 and later
10	25:7 mixed	Signed 25b filtered data filter[27:3] + signed 7b num_flux_jumps fj[6:0]. [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 50 MHz	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