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Part of the M Series Synchronization with LabVIEW and NI-DAQmx Example Set
E Series devices have been leading the market for data acquisition products for many years, and with the introduction of the new NI M Series devices, we feel strongly that NI multifunction data acquisition devices will continue to lead the market. As a result, it is important that current E Series users be able to use both E and M Series devices simultaneously. For this reason, this section presents the recommended method for synchronizing E Series and M Series devices.
E Series and M Series devices employ slightly different techniques for synchronization. To synchronize operations across multiple E Series devices, one device will export its 20 MHz master timebase to be used as the master timebase for the other devices. Although an E Series device can input a slower signal, such as 10 MHz, for its master timebase it cannot multiply that timebase up to re-create a 20 MHz timebase. Therefore, the resolution of the internal sample clocks that the E Series device could create by dividing down this external master timebase would be decreased. M Series devices cannot directly route out their internal 20 MHz timebase over the RTSI bus. M Series devices are able to directly route out only their 10 MHz reference clock. Therefore, the E Series device should be used as the master device when synchronizing an E Series and an M Series device. In this case, the E Series device can route out its 20 MHz master timebase to be used as the reference clock source for the M Series slave. The timebase on the M Series device would then be in phase with the 20 MHz master timebase of the E Series device.
Another behavior difference that must taken into account when synchronizing E and M Series devices is the difference in the default sample clock delay. The sample clock delay is the delay between when the AI Sample Clock occurs and when the first AI Convert Clock pulse for that scan occurs. With E Series, this default delay is 2 ticks of the master timebase, which is the minimum value allowed. With M Series, the default delay is 3 ticks of the timebase being used. Therefore, to more precisely synchronize an E Series device with an M Series device, change the E Series device to have a sample clock delay of 3 ticks. Figure 1 below demonstrates this behavior.
Figure 1 Default DelayFromSampleClk of E Series and M Series
Figure 2 is an example on how to synchronize an acquisition between an E Series and an M Series device.
Figure 2 E Series-M Series Synchronization
Example code from the Example Code Exchange in the NI Community is licensed with the MIT license.