Microblaze interrupt problem

hello,

  I have a microblaze system with a uart and a timer (both produce
interrupt).The interrupts are handled by intc.Uart interrupt is the
highest priority followed by timer interrupt.
1. can microblaze read only the required data from the uart at a
time.like say i want to get a frame from uart i.e data from one flag to
another flag and then stop reading the bytes fro uart.When i tried
doing this i realised that I have to read the whole file that i am
transferring from the hyperterminal to the uart.but i dont want this to
happen.any suggestions?
2. if the above behavior is not possible then i can send just one frame
at a time to uart from the hyperterminal.if i do this the what happens
is that my timer is also running at the same time.when it expires it
interrupts the microblaze.But now if i send a frame to uart,it
interrupts microblaze and then i stop getting interrupts from the
timer.if i send another file (data) from hyperterminal to uart,it
interrupts the microblaze properly but the timer has stopped
working or otherwise its interrupt is not getting recognised.
I thought that probably when i am in the uart_int_handler probably my
timer interrupt was genearted and it was missed since i was in int.
routine.Is this a possibility.?is yes ,how can i avoid this?I want to
service the timer interrupt after i return fro the uart handler.my intc
driver does not have XIN_SVC_ALL_ISRS_OPTION defined.so it does not
allow me to use it in the code.
Please share some information regarding this problem.
Thank you all.