Dear HugoPT,
I appreciate your help and thank you. 
However I don't think that solution may work. Here is the timing diagram provided in the data sheet.
In it, Sync line drops to low at the start of the data transmission and remains that way till all 24 bits are transmitted. If we transmit data as 3 separate words wont the that line becomes high three times ? The chip may think the signal is over only after the first 8bits.
(actually I tried transmitting data as 3 words one after another using buspirate.It too has a limit of 8bit word size. But didnt get any results. ) 
Is there any other suggestions ? Is there a configuration setting or something like that we can change ?
Thanks for the help HugoPT.
Gayan