www.pudn.com > the USB Simple Terminal example (PC Host Software > main1.a51

; This module initializes the microcontroller then executes MAIN forever 
; 
SignOnMessage:	DB 13, 13, "Serial1 V0.9", 13 	;USB Serial Device  
SignOnLength	EQU $-SignOnMessage 
 
Reset: 
	MOV	SP, #235		; Initialize the Stack 
	MOV	PageReg, #7FH		; Allows MOVX Ri to access EZ-USB memory 
 
	MOV	R0, #Low(USBControl)	; Simulate a disconnect 
	MOVX	A, @R0 
	ANL	A, #11110011b		; Clear DISCON, DISCOE 
	MOVX	@R0, A 
	CALL	Wait100msec   		; Give the host time to react 
	MOVX	A, @R0			; Reconnect with this new identity 
	ORL	A, #00000110b           ; Set DISCOE to enable pullup resistor 
	MOVX	@R0, A	 		; Set RENUM so that 8051 handles USB requests 
	CLR	A 
	MOV	FLAGS, A		; Start in Default state 
InitializeVariables: 
	MOV	R0, #SendBuffer 
	MOV	R7, BuffersLength 
IVLoop:	MOV	@R0, A			; Clear Send and Receive Buffers 
	INC	R0 
	DJNZ	R7, IVLoop 
 
	MOV	DPTR, #SignOnMessage	; Put a Signon in the Receive Buffer 
	MOV	R7, #SignonLength 
	MOV	R0, #ReceiveBuffer 
IVLoop2:MOVX	A, @DPTR 
	MOV	@R0, A 
	INC	DPTR 
	INC	R0 
	DJNZ	R7, IVLoop2 
	MOV	SerialIN, R0 
	MOV	USBout, #ReceiveBuffer 
	MOV	SerialOUT, #SendBuffer 
	MOV	USBin, #SendBuffer 
 
 
InitializeIOSystem:			; Work around the Dscope monitor I/O needs 
; Use Serial 0 since dScope has Serial 1 
	MOV	A, #0FFH		; Set up Timer 2 as a baud rate generator 
	MOV	T2High, A 
	MOV	T2Low, A 
	MOV	T2ReloadHigh, A 
	MOV	A, #0D9H		; 19.2Kb 
	MOV	T2ReloadLow, A 
	MOV	A, #00110100b 
	MOV	T2Control, A		; Start Timer 2 
	MOV	A, #01010000b		; Set up Serial 0 as 1 start, 8 data, 1 stop 
	MOV	S0Control, A 
 
InitializeInterruptSystem:		; First initialize the USB level  
	MOV	A, #00000000b 
	MOV	R0, #LOW(IN07IEN) 
	MOVX	@R0, A			; Enable EP1 IN Endpoints only 
	CLR	A 
	INC	R0 
	MOVX	@R0, A			; Disable interrupts from OUT Endpoints 0-7 
	INC	R0 
	MOV	A, #00000011b 
	MOVX	@R0, A			; Enable (Resume, Suspend,) SOF and SUDAV INTs 
	INC	R0 
	MOV	A, #00000001b 
	MOVX	@R0, A			; Enable Auto Vectoring for USB interrupts 
 
	MOV	R0, #LOW(EP1Control)	; Clear any stale information from ... 
	MOV	A, #00000010b		; ... EP1 IN buffer 
	MOVX	@R0, A 
	                                ; Now enable the main level 
	MOV	EIE, #00000001b		; Enable INT2 = USB Interrupt (only) 		 
        MOV	EI, #11010000b		; Enable Serial0 interrupt (and Ser1 for dScope) 
  
; Initialization Complete. 
;  
MAIN: 
	NOP				; Not much of a main loop for this example 
	JMP	MAIN			; All actions are initiated by interrupts 
; We are a slave, we wait to be told what to do 
 
Wait100msec: 
	MOV	Temp, #100 
Wait1msec:				; A delay loop 
	MOV	DPTR, #-1200		 
More:	INC	DPTR			; 3 cycles 
	MOV	A, DPL                  ; + 2 
	ORL	A, DPH                  ; + 2 
	JNZ	More                    ; + 3 = 10 cycles x 1200 = 1msec 
	DJNZ	Temp, Wait1msec 
	RET