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# SFRS_PEAKS1 specs
- 8x 50R SMA analog inputs
- inputs are for negative polarity detector pulses
- 8x analog channels, each comrising
- programmable attenuator, 0-31.5 dB
- inverting amplifier (gain=10) + fast leading edge discriminator
- amplitude to width converter
- 16x output channels to TDC (TAMEX4)
- out0 -> ch0 fast out
- out1 -> ch0 amplitude out
- out2 -> ch1 fast out
- out3 -> ch1 amplitude out
- out4 -> ch2 fast out
- out5 -> ch2 amplitude out
- [...]
- SFRS_PEAKS1 control registers are programmed by means of a tiny service python script:
~~~
# write argument order:
./pqdc1_spi.py <SFP> <device> <SPI chan> <register> <sub register> w <value>
# read back a value:
./pqdc1_spi.py <SFP> <device> <SPI chan> <register> <sub register> r 0
# example: set the fast discriminator threshold of the third channel (ch02) to 32000
./pqdc1_spi.py 1 0 0 0x00 2 w 32000
# example: set attenuation of the fifth channel (ch04) to 6 dB (factor 1/2)
./pqdc1_spi.py 1 0 0 0x02 4 w 12
note: SPI chan is always 0. There is only one FPGA on SFRS_PEAKS1 to choose from.
| Register Name | **SPI channel** | Register Address | **Sub Register** | Type | Description |
| ------------- | --------------- | ---------------- | ---------------- | ---------- | ----------------------------------------------------------------------------------------------------------------------------------------- |
| thr_FAST | 0 | 0x00 | 0-7 | 16 bit int | thresholds for the fast leading edge discriminator channels 0-7 |
| thr_AMP | 0 | 0x01 | 0-7 | 16 bit int | thresholds for the amplitude sampling channels 0-7 |
| att_setting | 0 | 0x02 | 0-7 | 6 bit int | attenuator settings for channels 0-7. 0.5 dB steps. A setting of 0 means no attenuation, a setting of 63 (max) means 31.5 dB attenuation. |
- The fast discriminator sees the output of the inverting amplifier, i.e. a signal with positive polarity. *Higher* threshold numbers means further away from the baseline. A good starting value is **thr_FAST** = 30000.
- The amplitude to width circuit sees the detector signal directly, i.e. a signal with negative polarity. *Lower* threshold numbers means further away from the baseline.
- If the amplitude to width circuit is not used, set **thr_AMP** to 65000.
- If the amplitude to width circuit shall be used, a good starting point is **thr_AMP** = 35000.