Delay between two write and read operation on serial port

[Toscan A.]

I'm using a PC serial line connected with k-line interface. The effect is that for each character that i send, there is the eco in rx.
A typical operation is: -write a byte on port
-wait the eco on receiver buff.
-read 1 byte in the buffer
I need to implement this operation several time but the delay between each phase (write-wait-read) is greater than 5ms.
For my application is very injurious.
I think that this problem depends on the serial vi given with LabView (5.1).
How can i read and write serial line without using this vi module?
Are there anyone that has given this problem?
Thanks

[Sanjay]

Can you set your serial hardware receiver to trigger on one byte received or, though worse, disable your serial hardware fifo/buffer?

[Toscan A.]

Thanks for your answere.
I have disable serial fifo and now the comunication
works without any delay.

[justing]

how did you disable the serial fifo buffer. I am having a delay problem myself. However, the delay occurs when my program enters a 6th level nested sequence structure. The delay is random though. Sometimes there is no delay other times it can be 600us. I really need to get rid of the delay. Thanks for an help