USART interrpt in PIC16F877A

Hi,
i have enabled USART interrupt in pic16f877a and it's interrupt work but other part of my program doesn't work.
im my program i read keyboard and when interrpt is coming it show the recieved data on lcd.
when serial data is coming the progran goes to interrupt and shoew the recieved data on lcd but reading keyboard doesn't work.
just the interrupt program is working.when i push the keys the program should show the number on lcd but it doesn't work and when i disable interrupt the keyboard program is working.
i enabled USART interrup like this:
on interrupt goto USART_int
INTCON = %11000000 'Initializing the INTCON register
PIE1= %00100000 'Initializing the PIE1 register
RCSTA= %11010011
and use this instruction :
serin PORTC.7,N1200,["A"],y1

could you help me?
what should i do?
maby i have a problem in my program.
i use micro code studio picbasic pro2.41



this is my program:

define OSC 4
include"modedefs.bas"
ADCON1=7 ' convert porta from analoge to digital
TRISA = %00000000 ' set porta as an output
TRISB = %00001111 'set first 4 bit of portb as an input and last 4 bit as putput
TRISC = %00000000 ' set portc as output
'----------------------------------------------------
' Define LCD parameters
' Set LCD Data port
DEFINE LCD_DREG PORTD
' Set starting Data bit (0 or 4) if 4-bit bus
DEFINE LCD_DBIT 4
' Set LCD Register Select port
DEFINE LCD_RSREG PORTD
' Set LCD Register Select bit
DEFINE LCD_RSBIT 1
' Set LCD Enable port
DEFINE LCD_EREG PORTD
' Set LCD Enable bit
DEFINE LCD_EBIT 0
' Set LCD bus size (4 or 8 bits)
DEFINE LCD_BITS 4
' Set number of lines on LCD
DEFINE LCD_LINES 2
'----------------------------------------------
y1 var byte
y2 var byte
y3 var byte
'-------------------------------------------------
on interrupt goto USART_int
INTCON = %11000000 'Initializing the INTCON register
PIE1= %00100000 'Initializing the PIE1 register
RCSTA= %11010011
'------------------------------------------------



scanning keyboard:


''program



goto scanning keyboard

USART_int:
disable
USART_int:
serin PORTC.7,N1200,["A"],y1
serin PORTC.7,N1200,["A"],y2
serin PORTC.7,N1200,["A"],y3
'
if (y2=y3) then
lcdout $fe,1,#y2
pause 4000
lcdout $fe,1
PORTC.4=1
pause 4000
PORTC.4=0
endif
INTCON = %11000000
PIE1= %00100000
RCSTA= %11010011
resume
enable
end
delay:
for i=1 to 2000
pause 1
next i
return

the program that i show you befor is an example but my main prigram is this that it is vey long.
about my hardware i connected keyboard to PORTB(row to RB0 to RB3 and
columns RB4 to RB7) and connect the RB0 to RB3 a 10k resister and i set the columns to 1 and read the rows rapidly to find which key is pushed.
i connected the DS1307 to RA0 and RA1(SDA to RA0 and SCL to RA1).
my program is about the reviever of a wireless weather station.
in my program i use haming codes to find and correct errors.
i connect a RF reciever to PORTC.7 but i my program it is on PORTA.5 that i corrert it in my harware and my software.
my program is very long abpot 1000 lines that i can't put it here and my keyboard program is long too and it has alot of subrotins.
what's the difference between serin and hserin instructions?

i found that two interrupts(USART and RB0) are working and when i turn on micro it goes to interrupt routine.
for RB0 i should connect a pull up resistor but when i connect the out put of the RF reciever to it interrupt occurs.
i don't know why?
maby the noise of RF reciever (when we don't have data) is the reason.
for USART interrupt ,i have the same problem but in this case , there is no deference between connecting and not connecting the RF reciever.
when i turn on micro it goes to interrupt routine.
what is the reason?
what should i do?

Hi,
i can solve my problem. it works but i have another problem.when i use this interrupt with a simple program it works but when i use this in a big one(my program is about 1000 lines) it doesn't work.
i also use 20M crystal but it doesn't work too.
what's the reason?

begin small. Have a look there
http://www.picbasic.co.uk/forum/show...1&postcount=11
and forget the SERIN stuff. Your PIC have an USART, use it with HSERIN or by reading RCREG