1) i need Assembly language documentation for C8051f350.

2)I need to toggle LED 1 using assembly language
when i execute this code in (The Silicon Laboratories IDE )show me error when using P0

//////////////////
BACK: MOV A,#00H
MOV P0,A
ACALL DELAY
MOV A,#0FFH
MOV P0,A
ACALL DELAY
SJMP BACK
;---------- this is delay subroutine ------------
ORG 300H
DELAY: MOV R5,#0FFH
AGAIN: DJNZ R5,AGAIN
RET
END

1) i need Assembly language documentation for C8051f350.
Read datasheet, rev.1.1, p89-91 and this link:
https://www.silabs.com/Marcom%20Documents/Training%20Videos/8051_Instruction_Set_Online_FINAL.pdf

2)I need to toggle LED 1 using assembly language
when i execute this code in (The Silicon Laboratories IDE )show me error when using P0
Which error? What means "using P0"? Using it in your code, or IDE port IO window?
Always post detailed information. Saying it doesn't work is only the half...
Your code has no comments. Currently, this is a small and easy piece of code, but for future please comment what your code is doing -> this is often helpful, because sometimes it shows you what you think the code should do, and helps to find out what the code is really doing.

I have C8051f350-TB...
Just to give you a example for the use of comments:
- I have to assume that your code posted above is complete and starting at 0x0000.
- I cannot locate the comment regarding the deactivation of the default enabled watchdog, and therefore I have to assume that your code will never work without deactivating the watchdog.
- ...

You see, comments might be helpful, at least for you, but surely for others to realize what your code does and what it should do.

Regards,

code????

last I heard code had indentions and comments

Take the advice of both scotty and erikm, cut and paste your code from the IDE to your post so everything your doing can be seen, errors often are found in the intialisation of the MCU which you have not given.
No matter how trivial the program always document/ use comments.
Indent by using the tab key and keep labels at the start of a block of code on a line by itself to make clear where the block of code starts. Neatness of code always makes it easier to follow.
I have cut and pasted Silicon Labs 'Blinky' program that is supplied with the developments kit as an example.

$NOMOD51
;-----------------------------------------------------------------------------
; Copyright (C) 2007 SILICON LABORATORIES, INC.
; All rights reserved.
;
; FILE NAME : F35x_BLINKY.ASM
; DATE : 06 FEB 04
; TARGET MCU : C8051F35x
; DESCRIPTION : This program illustrates how to disable the watchdog timer,
; configure the Crossbar, configure a port and write to a port
; I/O pin.
;
; NOTES:
;
;-----------------------------------------------------------------------------

$include (c8051f350.inc) ; Include register definition file.

;-----------------------------------------------------------------------------
; EQUATES
;-----------------------------------------------------------------------------

GREEN_LED equ P0.7 ; Green LED: '1' is ON

;-----------------------------------------------------------------------------
; RESET and INTERRUPT VECTORS
;-----------------------------------------------------------------------------

; Reset Vector
cseg AT 0
ljmp Main ; Locate a jump to the start of
; code at the reset vector.

;-----------------------------------------------------------------------------
; CODE SEGMENT
;-----------------------------------------------------------------------------

Blink segment CODE

rseg Blink ; Switch to this code segment.
using 0 ; Specify register bank for the
; following program code.

Main:
; Disable the WDT.
anl PCA0MD, #NOT(040h) ; clear Watchdog Enable bit

; Enable the Port I/O Crossbar
mov XBR1, #40h ; enable Crossbar
orl P0MDOUT, #80h ; make LED pin output push-pull
orl P0MDIN, #80h ; make LED pin input mode digital

; Initialize LED to OFF
clr GREEN_LED

; Simple delay loop.
Loop2: mov R7, #03h
Loop1: mov R6, #00h
Loop0: mov R5, #00h
djnz R5, $
djnz R6, Loop0
djnz R7, Loop1
cpl GREEN_LED ; Toggle LED.
jmp Loop2

;-----------------------------------------------------------------------------
; End of file.

END

Unfortunatley this cut and paste has taken all the indentation/alignment out and Iam not smart enough to know if it is possible to cut and paste whilst keeping it in!!
Iam sure someone can show me.:-)

Mike

I solved my error

see my code
//////////////

P0MDOUT  DATA   0A4H   ; PORT 0 OUTPUT 
PCA0MD  DATA   0D9H   ; PCA MODE
XBR1    DATA   0E2H   ; PORT I/O CROSSBAR CONTROL 1 
ANL  PCA0MD,  #NOT(040h)   ; clear Watchdog Enable bit
 
 ; Enable the Port I/O Crossbar
      MOV   XBR1, #40h      ; enable Crossbar
      ORL   P0MDOUT, #0C0h  ; make LED pin output push-pull
           
 
MAIN:ACALL DELAY
     cpl   80H.7               ; Toggle LED.
     jmp   MAIN

;---------- this is delay subroutine ------------
ORG 300H
DELAY:      mov   R3, #05h	
AGAIN1:     mov   R2, #00h
AGAIN0:     mov   R1, #00h
            djnz  R1, $
            djnz  R2, AGAIN0
            djnz  R3, AGAIN1
	    RET
END

NO, don't do that! The forum (and html) will not know what to do with them. Always use spaces to indent when posting to this (any?) forum.

Unfortunatley this cut and paste has taken all the indentation/alignment out and I am not smart enough to know if it is possible to cut and paste whilst keeping it in!!
I am sure someone can show me.:-)

For the umpteenth time: put the code between <pre> and </pre> to preserve the indentation in this (any?)forum.

Btw. "I" and "am" are two words.