Dual Channel Operation

Trace modes TM1, TM3 and TM4 can be set up to capture data from two inputs.

About Trace Channels...

BitScope has one A/D convertor but 2 trace channels; one called primary, the other secondary. Trace channels are key to dual channel operation. They control the input selection and attenuation for each channel of analog data that is recorded.

Register R14 contains two sets of control bits; one for the primary, the other for the secondary. The settings are independent of each other; they can even be set the same.

Trace modes TM0 and TM2 capture data using the primary channel only. Modes TM1, TM3 and TM4 use both channels. All modes trigger on the primary channel only.

Dual Channel (ALT)

Trace mode TM1 captures two inputs using a technique similar to ALT MODE on an analog oscilloscope. It allows both channels to captured relative to a trigger event occuring on the primary channel.

When both analog inputs are connected to phase related periodic waveforms, it is possible to capture continuous segments from each while maintaining their phase relationship.

TM1 allows BitScope to capture a buffer from the primary channel and then one from the secondary channel, both referenced to the same trigger event, for subsequent display together.

Dual Channel (CHOP)

Of course, your analog oscilloscope also has CHOP MODE to show two channels, and so does BitScope.

In this case, trace modes TM3 and TM4 support channel chopped data capture. That is, the primary and secondary trace channel are swapped repeatedly after a trigger event on the primary channel, so the captured data contains a series of alternating sample sets from the primary and secondary channels.

Normally each trace channel will be programmed for a different input and/or attenuation range, as approprate for the system under test.

However, it is of course also possible to program both the primary and secondary channels with the same settings, in which case channel chop reverts to single channel capture. Use this technique if you want to capture one channel with a slow clock.