Thanks for the reply but maybe my question was not clear.
As @attila said, SPI protocol can send 16k bits length of data. However, what I have to do is send lots of SPI commands each consisting of 32-bit and precisely configure the interval between them. To do so, I'm using a pattern generator of AD2 as the figures below.
As the interval between CS low edge (except between the first and second) should be an integer multiple of 40.96 microseconds in my application, I adjusted the clock frequency and inserted several bits between them and this is okay. And I want the first pattern comes 30 times repeatedly and then the second pattern comes. Repetition is done simply by setting the pattern generator's repeat count to 30. But it was not able to hardcode all the patterns in a 16k bits buffer, so I separated them.
The problem is that when I tried to run the application by the script above, the interval between pattern 1 and pattern 2 is not an integer multiple of 40.96 microseconds.
Also, it seems that when I run a pattern generator, another one becomes a busy state. Is it okay?