Hi,
I have connected red Led's to p1.0 to P1.7.A resistance of 270 Ohms is connected on everey led in this way.Cathode of led to resistance and then resistance to port pin.anode of every led to Vcc 5 volts.
I have done the above on p1.0-p1.7
I am using 12 Mhz crystal,Max232 for serial port.The communication is taking place.But if at a time more than 6 leds cannot be turned on.if i do so all turn off or the controller hangs.Then i have to reset it.

controller code
baudnum equ 0f3h ;no loaded in th1 for 2403.8 baud
org 0000h
anl pcon,#7fh ; set smod bit to 0 for baud*32 rate
anl tmod,#30h ;alter timer t1 config only
orl tmod,#20h ;set timer t1 as 8 bit auto reload
mov th1,#baudnum ;th1 set for divide clock by 13d
setb tr1 ;t1 running at 1e6/13=76923Hz
mov scon,#40h ;uart mode 1
setb ren ;for recving enable ren bit
here:
jbc ri,receive ;loop until char recd
sjmp here ;poll ri again
receive:
clr ri ;clr ri to prevent false read
mov a,sbuf ;sbuf gets val like 1h if p1.0 is to be lit up,if p1.0 and p1.1 has to be lit up the it will get 3h,if p1.0,p1.1,p1.2 has to be lit up sbuf will have 7h.for p1.0 to p1.3 sbuf will have 15h and so on

cpl a
mov p1,a
sjmp here
end