The fastest you can update one channel on the NI-9476 is every 500us because of the propagation delay. Normally, this is the specification that we want to look at because it indicates how often we can change the state of the signal in one channel. This is why this is the value shown in the Digital Output Module Comparison Table.
However, the update rate for the serial communication of the module is 40us, which means that you can send an update command every 40us.
- For example, if you want to update CH0 from low to high or vice versa, then you will have to wait for 500us to change it back because of the propagation delay, but you can update CH1 (or a different channel) as quickly as 40us after you send the first update.
This is why you might receive a warning when setting up a hardware-timed task running at more than 2 kHz (500us) for one channel.