The 32-bit counter counts up or down synchronously with the Source signal/counter timebase. The other counter inputs are asynchronous to this signal, so the TestScale backplane synchronizes these signals before presenting them to the internal counter.

Depending on how you configure your backplane, the TestScale backplane uses one of two synchronization methods:

  • 80 MHz Source Mode
  • External or Internal Source Less than 20 MHz

80 MHz Source Mode

In 80 MHz source mode, the backplane synchronizes signals on the rising edge of the source, and counts on the third rising edge of the source. Edges are pipelined so no counts are lost, as shown in the following figure.

Figure 50. 80 MHz Source Mode


External or Internal Source Less than 20 MHz

With an external or internal source less than 20 MHz, the backplane generates a delayed Source signal by delaying the Source signal by several nanoseconds. The backplane synchronizes signals on the rising edge of the delayed Source signal, and counts on the following rising edge of the source, as shown in the following figure.

Figure 51. External or Internal Source Less than 20 MHz