Input Selection

The frequency to measured may be observed from four possible inputs:

  1. ADC input.
  2. Logic data signal bit 7.
  3. 1 GHz Pre-scaler input.
  4. Any trigger event or signal on any logic input.

Spock option register bits R7:2/1 are programmed to select the input:

Bit NameValue Meaning

2/1Trig Bit 7 MUX0 DD7 : Digital Data Bus Bit 7.
1 Comparator : trigger match comparator signal.
2 Event 1 : (Pre-scaler output frequency halved).
3 Event 2 : (ADC input frequency halved).

If the ADC input is selected the Input/Attenuation Register R14 also must be programmed to select the appropriate input and level attenuation for the primary trace channel.

The secondary trace channel is not used.