assembly help please..

i am an assembly newbie. anybody could please help me realize the output of the following code?

ORG 0000H
SJMP START
ORG 000BH
SJMP TIMER0
ORG 0030H
START: MOV SP,#60H
MOV A,#0FFH
MOV P1,A

MOV TMOD,#06H
MOV TH0,#255
MOV TL0,#255
SETB ET0
SETB TR0
SETB EA
SJMP $

TIMER0: CLR TR0
CLR C
RLC A
CJNE A,#00H,SKIP
MOV P1,A
MOV A,#0FFH
JMP SKIP1

SKIP: MOV P1,A

SKIP1: SETB TR0
RETI
END

Apparently, this will output the following sequence on the port 1:

0xff,0xfe,0xfc,0xf8,0xf0,0xe0,0xc0,0x80,0x00,0xfe,0xfc,0xf8... and so on.

The update rate is depending on the CPU clock.

/pisoiu

pisoiu said:

Apparently, this will output the following sequence on the port 1:

0xff,0xfe,0xfc,0xf8,0xf0,0xe0,0xc0,0x80,0x00,0xfe,0xfc,0xf8... and so on.

The update rate is depending on the CPU clock.

/pisoiu

Click to expand...

thank you so much.. but, please, I truly cannot get it. actually how would it look like? appreciate it so much.:|

Judging after the value loaded in TMOD, the actual settings for timer is to run as an external event counter. So, the sequence I was talking about is triggered not by an interval, but by an external event. You may have there a push button or a sensor of some kind.
The sequence on the port is simple to understand if you convert from hex to binary, and it will look like this:
0xff=11111111
0xfe=11111110
0xfc=11111100
0xf8=11111000
0xf0=11110000
0xe0=11100000
0xc0=11000000
0x80=10000000
0x00=00000000
0xfe=11111110
and so on

Most probably, on each pin of P1 is a LED connected. If the led is connected between pin and +, the led will lit when the bit is 0. If the led is between pin and ground, it will lit with bit=1
So the end result is to walk through that sequence when the external bit receives a signal.

your program will respond to pulse applied to your uC T0 pin. when a pulse apllied, it will roll the value on port1. any way you won't notice it cos, the clock frequencies is too high. try to add some delay instruction.