The three general purpose counters on the DAQcard-1200 can all be used for square wave generation. However, as you question is hinting on, only the first counter can be used with an internal clock. For these applications, the CLK and GATE signals at the
front I/O connector control the counters. The single exception is counter B0, which has an internal 2 MHz clock. You must use signals connected to the I/O Connector to provide the necessary signals to your other counters.
Jared A