如何修改 USB-6501 数字输出一串序列的频率? How to change the freq. of USB-6501 Digital Output ? (VB6)

[UUFFOO]

For i = 0 To 9
     bit(i) = i Mod 2
Next
DAQmxErrChk DAQmxWriteDigitalLines(thSDA_O, 10, 1, 5#, DAQmx_Val_GroupByChannel, bit(0), tmp1, ByVal 0&)

用VB6产和5个脉冲(10个电平), 示波器如下:

the wave figure below:

You can see , the rare=1K, How can change the Rate=10K ?

可以看到, 上面的宽度为1ms (周期=2ms), Sample Rate=1K

我想改为10K, 不知怎么改? 

You can see , the rare=1K, How can change the Rate=10K ?

我用了这个命令: 

DAQmxErrChk DAQmxCfgSampClkTiming(thSDA_O, "", 10000, DAQmx_Val_Falling, DAQmx_Val_AcquisitionType_ContSamps, 1000)

但是给出一个错误提示:

是我做错了? 还是USB-6501不支持修改采样率? 

Am I wrong , Or  USB-6501 doesnot support changing  Sample Rate ????