Raw-mode readout

Raw data refers to 50MHz ADC samples. The memory available in MCE to store such data is 8192x8 bits. Hence, the 14-bit ADC samples are pre-scaled by 1/2⁶ and the resulting signed 8b number is reported as usual signed 32b.

Raw data acquisition is only available in certain build of readout-card firmware. The latest firmware to support raw mode is: 0x04010017.

(Raw data acquisition and 4-pole low-pass filter are both memory-intensive features of the MCE readout-card firmware. As a general rule, a given firmware has only one of these features available, e.g., the firmware that has raw mode enabled will not include the filter and vice versa. In some versions that support raw mode, read back of gaini0/gainp0/gaind0 is also not supported.)

Setup

There are two MCE parameters that have to be set for raw data acquisition:

captr_raw stores a snapshot of row_len samples of num_rows rows for 2 consecutive frames up to 8192 entries for each channel and stores them in MCE memory buffer for readout in raw mode.

data_mode determines the pixel-data readout mode. data mode has to be set to 3 for raw mode.

A typical sequence of commands for data acquisition is:

 wb cc ret_dat_s 1 1
 wb rc1 data_mode 3
 wb rc1 captr_raw 1
 acq_config filename rc1
 acq_go row_len*2

Side effects

Filter mode is typically not available in firmware that supports raw mode.

Considerations

1) Once the raw-buffer of 8192x8b is full, no more samples are stored till a new captr_raw is issued.

2) The raw-buffer is shipped out of MCE in a regular frame format (header + num_rows_reported*num_columns + checksum). As compared with normal MCE flatfile data organization, in raw mode the time index takes the place of row. At each time, all columns are reported.

For rc1 only, for example, time indices t = [0, num_rows_reported-1] are reported in the first frame, with the offset of column c and time t being

index = t*8 + c

Subsequent frames contain subsequent data samples. Since the number of time samples, per column, in a full multiplexing cycle of the MCE is row_len*num_rows, the number of readout frames required to record an entire MCE internal frame's-worth of raw data is equal to row_len (assuming that num_rows = num_rows_reported).

The readout frame and index of a given time t, column c, is thus

frame = floor[ (t*8 + c) / num_rows_reported ]
index = (t*8 + c) mod num_rows_reported

Since the number of clock ticks spent on each row is row_len, the row associated with time t is

row = floor [ t / row_len ]

It is possible to get raw mode data from multiple readout cards; in that case the data will be packaged in the usual way, with all columns reporting at each time.

Schematically, the organization of raw data for num_rows = num_rows_reported = 33 and row_len = 100 can be represented as follows (here sNNNNNcXX represents a word containing the data for time sample NNNNN, column XX):

(header of frame 0, 43 words)
s0000c00 s0000c01 s0000c02 s0000c03 s0000c04 s0000c05 s0000c06 s0000c07
s0001c00 s0001c01 s0001c02 s0001c03 s0001c04 s0001c05 s0001c06 s0001c07
s0002c00 s0002c01 s0002c02 s0002c03 s0002c04 s0002c05 s0002c06 s0002c07
...
s0032c00 s0032c01 s0032c02 s0032c03 s0032c04 s0032c05 s0032c06 s0032c07
(checksum of frame 0, 1 word)

(header of frame 1, 43 words)
s0033c00 s0033c01 s0033c02 s0033c03 s0033c04 s0033c05 s0033c06 s0033c07
...
s0065c00 s0065c01 s0065c02 s0065c03 s0065c04 s0065c05 s0065c06 s0065c07
(checksum of frame 1, 1 word)

...

(header of frame 199, 43 words)
s6567c67 s6567c01 s6567c02 s6567c03 s6567c04 s6567c05 s6567c06 s6567c07
...
s6599c00 s6599c01 s6599c02 s6599c03 s6599c04 s6599c05 s6599c06 s6599c07
(checksum of frame 199, 1 word)

3) Unfortunately, collecting data for up to 2 internal MCE frames is hard-coded in firmware. Even if you reduce number of rows, you will be restricted by 2 frames. If you really want to look at more samples, then you may want to increase row_len instead and using row_order parameter of the address card, move your particular row of interest to the beginning of the frame.

4) readout_row_index parameter is ignored when data_mode is set to 3 or raw mode.

5) if num_rows_reported < num_rows, it takes more frames (to be exact: n = (num_rows*row_len*2/num_rows_reported) frames) to read all the data out.