bootloader_gnu.s

Sharp LH75401(ARM7)处理器部分控制程序。

/*;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; 
 ; $Workfile:   bootloader_gnu.s  $ 
 ; $Revision:   0.00  $ 
 ; $Author:     AnvikE  $ 
 ; $Date:       Mar 06 2003   $ 
 ; 
 ; Project:     LH754XX
 ; 
 ; Description: 
 ;  This file is a implementation file for KEV754XX chip boot code.
 ; 
 ; Revision History: 
 ; 				
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;  
 ; 
 ;  Copyright (c) 2002 Sharp Microelectronics of the Americas 
 ; 
 ;  All rights reserved 
 ; 
 ;  SHARP MICROELECTRONICS OF THE AMERICAS MAKES NO REPRESENTATION 
 ;  OR WARRANTIES WITH RESPECT TO THE PERFORMANCE OF THIS SOFTWARE, 
 ;  AND SPECIFICALLY DISCLAIMS ANY RESPONSIBILITY FOR ANY DAMAGES, 
 ;  SPECIAL OR CONSEQUENTIAL, CONNECTED WITH THE USE OF THIS SOFTWARE. 
 ; 
 ;  SHARP MICROELECTRONICS OF THE AMERICAS PROVIDES THIS SOFTWARE SOLELY 
 ;  FOR THE PURPOSE OF SOFTWARE DEVELOPMENT INCORPORATING THE USE OF A 
 ;  SHARP MICROCONTROLLER OR SYSTEM-ON-CHIP PRODUCT. USE OF THIS SOURCE 
 ;  FILE IMPLIES ACCEPTANCE OF THESE CONDITIONS. 
 ; 				
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;*/	
	.TEXT
	.CODE 32
	.INCLUDE "bootloader_gnu.h"
	.GLOBAL   __start	/* export entry point to the linker   */
	.EXTERN   __end		/* linker defined end of boot code    */
	/* The code starts here */	
__start:
	/*
	 * This is the location of the required interrupt
	 * vectors that are used by the arm core to handle
	 * system faults.
	 */

	
	B   resetHandler	/* run out of the ROM		      */
	B   undefHandler 	/* 0x04 - undefined instruction       */	
	B   swiHandler		/* 0x08 - software interrupt          */
	B   prefetchHandler	/* 0x0C - prefetch abort              */
	B   abortHandler	/* 0x10 - data abort                  */
	NOP                     /* reserved vector                    */
        LDR pc, [pc, #-0xFF0]   /* 0x18 VIC IRQ */
fiqHandler:	
undefHandler:
swiHandler:
prefetchHandler:
abortHandler:
	/* 
	 * All exceptions are handled by a default handler for now. 
	 * The user or operating system can add functionality at 
	 * run time if they wish. 
	 * Note: To install handlers at a later time requires that 
	 * the system have volatile memory mapped to 0. This can be 
	 * accomplished via the remap register.
	 */
	B   faultHandler

resetHandler:	
	/* 
	 * This section set up the system clocks to 51.6MHz 
	 */
	MOV	r0, #RCPC_SYSCLK_PRESCALE_DEFAULT
	LDR	r1, =RCPC_REG_BASE
	STR	r0, [r1,#RCPC_SYSCLK_PRESCALE_OFFSET]

	/* 
	 * This section inits all of the stacks for the different modes
	 * that the arm core can run in (IRQ, SVC mode etc ...)
	 * Note: All of individual mode stacks point to the same 
	 * location in TCM memory. This was done for simplicity since 
	 * there is no exception handler installed, this can be done by 
	 * the user or an operating system at run time. The fault 
	 * handler basically sets up the timer and goes back to blinking 
	 * the led in the at the idle loop. If the user breaks in with 
	 * debugger after an exception they can look at the lrm and sp 
	 * to determine which execption took place, and where the stack 
	 * pointer was when the fault happened.
	 */
modeInit:
	/* All interrupts disabled at core                            */	
	MOV	r1, #I_MASK
	ADD     r1, r1, #F_MASK	

	/* Enter IRQ mode and setup the IRQ stack pointer             */
	ORR	r0, r1, #MODE_IRQ	
	MSR	cpsr_cxsf, r0
	LDR	r13, =EXCEPTION_STACK
	
	/* Enter FIQ mode and setup the FIQ stack pointer             */
	ORR	r0, r1, #MODE_FIQ 	
 	MSR	cpsr_cxsf, r0
	LDR	r13, =EXCEPTION_STACK
	
	/* Enter Abort mode and setup the Abort stack pointer         */
	ORR	r0, r1, #MODE_ABORT	
	MSR	cpsr_cxsf, r0
	LDR	r13, =EXCEPTION_STACK
	
	/* Enter Undefined mode and setup the Undefined stack pointer */
	ORR	r0, r1, #MODE_UNDEF	
	MSR	cpsr_cxsf, r0
	LDR	r13, =EXCEPTION_STACK

	/* Enter System mode and setup the User/System stack pointer  */
	ORR	r0, r1, #MODE_SYSTEM	
	MSR	cpsr_cxsf, r0
	LDR	r13, =EXCEPTION_STACK

	/* Enter SVC mode and setup the SVC stack pointer             */
	ORR	r0, r1, #MODE_SVC		
	MSR	cpsr_cxsf, r0
	LDR	r13,=EXCEPTION_STACK

	/* 
	 * We are now running in service mode and it is time to set up 
	 * external memory and chip selects
	 */
memoryInit:
	/* Set up the external bus interface                          */
	LDR	r0, =EBI_MUX_BASE	/* base address of ebi	      */
	LDR	r1, =EBI_PIN_CONFIG	/* config for 3 CS's etc      */
	STR	r1, [r0, #0]		/* m[0xFFFE5000] <- d[0x5B3F] */

	/* Set up chip selects */
	LDR	r0, =SMC_REG_BASE	/* base address of SMC        */

	/* Setup Flash BCR0 on CS0                                    */
	LDR	r1, =SMC_BCR0_INIT	   /* reg setting for Flash   */
	STR	r1, [r0, #SMC_BCR0_OFFSET] /* d[0x1C001481]           */ 

	/* Setup SRAM BCR1 on CS1                                     */
	LDR	r1, =SMC_BCR1_INIT	   /* reg setting for Sram    */
	STR	r1, [r0, #SMC_BCR1_OFFSET] /* d[0x10000000]           */

	/* Setup Memory mapped BCR2 on CS2                            */
	LDR	r1, =SMC_BCR2_INIT	   /* register settings       */
	STR	r1, [r0, #SMC_BCR2_OFFSET] /* d[0x10000C21]           */

bootcodeCopy:	
	/*
	 * Now that the memory controller is set up we want to make a 
	 * copy of this boot code in internal ram. We are doing this 
	 * so we can use the remap register to remap flash to 
	 * 0x60000000, and internal sram to 0. This allows the c 
	 * applications to install interrupt vectors at 0. So after we 
	 * remap the memory space we better have a shadow copy of this 
	 * boot code at 0 or we are going to go off into the weeds.
	 */
	LDR	r0, =__start		/* source		      */
	LDR	r1, =INTERNAL_SRAM_BASE	/* destination                */
	LDR	r2, =__end		/* end                        */
codeCopy:	
	LDR	r3, [r0]	/* move the opcode from rom           */
	STR	r3, [r1]	/* move the opcode to internal memory */
	CMP	r0, r2           
	BEQ	switchCheck	/* are we done the copy yet	      */
	ADD	r0, r0, #4	/* increment source pointer           */
	ADD	r1, r1, #4      /* increment destination pointer      */
	B	codeCopy

switchCheck:
	/*
	 * Now we are going to check the switch on the user board to 
	 * determine if we are going to execute a user application or 
	 * go to the idle loop where we sit a blink the green led.
	 * Switch Mappings:
	 * 1 - ON - copy code from sector 0x02 to 0x44000000
	 * 2 - ON - copy code from sector 0x01 to 0x44000000
	 */
	LDR	r0, =DIP_SWITCH_ADRS /* set up the switch base addr   */
	LDRB	r1, [r0, #0]	     /* get the switch cur setting    */

	/* Run the Angel application                                  */
	MOV	r2, #ANGEL_DEMO
	LDR	r0, =ANGEL_APP_BASE
	LDR	r3, =ANGEL_APP_SIZE
	MOV	r4, #0x01	
	LDR	r5,	=ANGEL_ENTRY
	CMP	r1, r2
	BEQ	appLoadInit

	/* Run the User demo application                              */
	MOV	r2, #USER_DEMO
	LDR	r0, =USER_APP_BASE
	LDR	r3, =USER_APP_SIZE
	MOV	r4, #0x01	
	LDR	r5,	=USER_ENTRY
	CMP	r1, r2
	BEQ	appLoadInit
	MOV	r4, #0
	B	memoryRemap	
	
appLoadInit:
	MOV	r1, r5		/* destination in Sram                */
	MOV	r2, r3		/* Max number of bytes per demo       */
	ADD	r2, r2, r0      /* The end address of the demo        */

appLoad:
	LDR	r3, [r0]	/* move the opcode from rom           */
	STR	r3, [r1]	/* move the opcode to external memory */
	CMP	r0, r2           
	BEQ	memoryRemap	/* are we done the copy yet	      */
	ADD	r0, r0, #4	/* increment source pointer           */
	ADD	r1, r1, #4	/* increment destination pointer      */
	B	appLoad
	
memoryRemap:	
	/* 
	 * We are now remapping the memory chip selects so that it 
	 * will look like the memory for flash has been mapped to 
	 * 0x40000000 and internal sram is mapped to 0.
	 */
	LDR	r0, =RCPC_REG_BASE	
	MOV	r1, #RCPC_REMAP_INTERNAL_RAM
	STR	r1, [r0, #RCPC_REMAP_OFFSET] /* d[0x00000002]         */
			
	/* 
	 * Now lets set up the c stack and put the current mode stack 
	 * (service mode) at the top of external SRAM. The c startup 
	 * code should take care of this but ya never know, and 
	 * besides it won't hurt.
	 */
	LDR	r13,=C_STACK

demoExecute:	
	/* 
	 * Now that we are ready to go to the idle loop, lets see if 
	 * the user dip switch has been set to user demo mode.
	 * Note: The switch state of 1 means that we should execute 
	 * from 0x44000000. This value was saved in r4
	 */
	MOV	r0, #1
	CMP	r0, r4
	BNE	idleLoopStart
	MOV	pc, r5 

idleLoopStart:	
	/*
	 * The rest of the code sets up a timer compare register and 
	 * spins on the counter until it gets a compare match. Once the 
	 * compare match is determined the green led on the board is 
	 * toggled between the on/off state.
	 */
timerInit:		
	/* set up Port D Bit 1 as an output                           */
	MOV	r0, #GPIO_D1		/* GPIO base address in r3    */
	LDR	r3, =GPIO_REG_BASE		
	STR	r0, [r3,#GPIO_PDDDR_OFFSET]

	/* Configure Timer 0 to be clocked as slowly as possible      */
	LDR	r1, =TIMER0_REG_BASE	/* base addr TIMER0 in r1     */ 
	MOV	r0, #TIMER0_CTRL_INIT	
	STR	r0, [r1, #TIMER0_CTRL_REG_OFFSET]
	MOV	r2,#TIMER0_STATUS_CMP1    

ledToggle:	
        LDR     r0,[r3,#GPIO_PDDR_OFFSET]
        EOR     r0,r0,#GPIO_D1
	STR     r0,[r3,#GPIO_PDDR_OFFSET]

	/* wait for TIMER0 compare match                              */
idleLoop:	
	LDR     r0,[r1,#TIMER0_STATUS_REG_OFFSET]
	TST     r0,r2
	BEQ     idleLoop		

	/* At compare match clear the count                           */
	LDR     r0,[r1,#TIMER0_CTRL_REG_OFFSET]
	ORR     r0,r0,#TIMER0_CTRL_COUNT_CLEAR
	STR     r0,[r1,#TIMER0_CTRL_REG_OFFSET]

	/* 
	 * now that there is no compare match, clear the compare 
	 * match status 
	 */
	STR     r2,[r1,#TIMER0_STATUS_REG_OFFSET]
	B	ledToggle

faultHandler:	
	B       timerInit	/* spin                               */
	.END