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 + 41x8 + checksum). So the order of data is as follows: (r0c0s0 refers to "row 0, column 0, sample 0")

bla bla ...

3) Unfortunately, collecting data for up to 2 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.