You can use the 8255 port of a 6025 with handshaking to in essence accomplish hardware timed DIO to a sample clock. To do this, wire the sample clock up to one of the handshaking signals and leave the other handshaking signal unwired. Which handshaking signals you need to use depend on the port and direction, but you can check the user manual for more documentation. The main drawbacks to this approach are that you can't go very fast and there is no way to know if you missed a clock. You can't go very fast because each clock edge of the handshaking signal generates an interrupt on the device. This generally limits your throughput to a few kS/s since your computer has to handle and process thousands of interrupts per second. Also, since there is no FIFO or other circuitry on the board to detect multiple clocks before a read or write occurs, it's possible you will miss samples without receiving any notification from the driver as your sample clock increases in frequency. Generally this isn't an issue with handshaking because the feedback handshaking signal self regulates the speed of the acquisition. However, as I stated above, to achieve sample clock like behavior, this signal must be left unconnected.
There are a couple of other boards that are supported under Traditional DAQ you can use that have correlated digital functionality similar to M Series. The 673x AO Waveform boards and the 6115/6120 S Series boards both have 8 lines of correlated digital I/O. They aren't MIO boards, but perhaps they will work for you. These boards along with the 653x high speed digital boards are supported under both Traditional DAQ and DAQmx.
