S3C2410 clock and timer

Directly use the external clock source

Select by setting the pin

FCLK  cpu

HCLK  AHB

PCLK  APB

PLL increases the system clock speed through the clock control logic PLL

UPLL  USB

MPLL  FCLK HCLK PCLK

PLL is not started FCLK=Fin (crystal frequency)

The s3c2410 has five 16-bit timers,  of which the first four timers have PWM function  , that is, an output pin  can be controlled by the timer to periodically high or low levels. The clock source of the timer is PCLK

@**********************************************************************************
@ File: head.S
@ Function: Initialize, set the interrupt mode, system mode stack, and interrupt handling function
@******************************************************************************       
  
.extern     main
.text
.global _start
_start:
@**********************************************************************************       
@ Interrupt vector. In this program, except Reset and HandleIRQ, other exceptions are not used
@******************************************************************************       
   b   Reset

@ 0x04: The vector address of the undefined instruction abort mode
HandleUndef:
   b   HandleUndef
 
@ 0x08: The vector address of the management mode, which is entered by the SWI instruction
HandleSWI:
   b   HandleSWI

@ 0x0c: vector address of the exception caused by instruction prefetch termination
HandlePrefetchAbort:
   b   HandlePrefetchAbort

@ 0x10: The vector address of the exception caused by data access termination
HandleDataAbort:
   b   HandleDataAbort

@ 0x14: Reserved
HandleNotUsed:
   b   HandleNotUsed

@ 0x18: interrupt mode vector address
   b   HandleIRQ

@ 0x1c: Vector address of fast interrupt mode
HandleFIQ:
   b   HandleFIQ

Reset:                  
   ldr sp, =4096           @ Set the stack pointer. The following are all C functions. You need to set the stack before calling
   bl  disable_watch_dog   @ Turn off WATCHDOG, otherwise the CPU will restart continuously

   bl  clock_init          @ Set up MPLL, change FCLK, HCLK, PCLK

   bl  memsetup            @ Set up the memory controller to use SDRAM
   bl  copy_steppingstone_to_sdram     @ Copy code to SDRAM
   ldr pc, =on_sdram                   @ Jump to SDRAM and continue execution
on_sdram:
   msr cpsr_c, #0xd2       @ Enter interrupt mode
   ldr sp, =4096           @ Set interrupt mode stack pointer

   msr cpsr_c, #0xdf       @ Enter system mode
   ldr sp, =0x34000000     @ Set the system mode stack pointer,

   bl  init_led            @ Initialize the GPIO pin of LED

   bl  timer0_init         @ Initialize timer 0  

   bl  init_irq            @ Call the interrupt initialization function in init.c
   msr cpsr_c, #0x5f       @ Set I-bit=0, open IRQ interrupt
   
   ldr lr, =halt_loop      @ Set the return address
   ldr pc, =main           @ Call the main function
halt_loop:
   b   halt_loop

HandleIRQ:
   sub lr, lr, #4                  @ Calculate the return address
   stmdb   sp!,    { r0-r12,lr }   @ Save the used registers
                                   @ Note that sp at this time is the sp of interrupt mode
                                   @ The initial value is 4096 set above
   
   ldr lr, =int_return             @ Set the return address after calling ISR, i.e. EINT_Handle function 
   ldr pc, =Timer0_Handle          @ Call interrupt service function, in interrupt.c
int_return:
   ldmia   sp!,    { r0-r12,pc }^  @ Interrupt return, ^ means copy the value of spsr to cpsr

#include "s3c24xx.h"
 
void disable_watch_dog(void);
void clock_init(void);
void memsetup(void);
void copy_steppingstone_to_sdram(void);
void init_led(void);
void timer0_init(void);
void init_irq(void);

void disable_watch_dog(void)
{
   WTCON = 0;  // It is very simple to turn off WATCHDOG, just write 0 to this register
}

#define S3C2410_MPLL_200MHZ     ((0x5c<<12)|(0x04<<4)|(0x00))
#define S3C2440_MPLL_200MHZ     ((0x5c<<12)|(0x01<<4)|(0x02))

void clock_init(void)
{
   // LOCKTIME = 0x00ffffff;   // Use the default value
   CLKDIVN  = 0x03;            // FCLK:HCLK:PCLK=1:2:4, HDIVN=1,PDIVN=1

   
__asm__(
   "mrc    p15, 0, r1, c1, c0, 0n"        
   "orr    r1, r1, #0xc0000000n"          
   "mcr    p15, 0, r1, c1, c0, 0n"        
   );

   
   if ((GSTATUS1 == 0x32410000) || (GSTATUS1 == 0x32410002))
   {
       MPLLCON = S3C2410_MPLL_200MHZ; 
   }
   else
   {
       MPLLCON = S3C2440_MPLL_200MHZ; 
   }       
}

void memsetup(void)
{
   volatile unsigned long *p = (volatile unsigned long *)MEM_CTL_BASE;

   
   
   p[0] = 0x22011110;     //BWSCON
   p[1] = 0x00000700;     //BANKCON0
   p[2] = 0x00000700;     //BANKCON1
   p[3] = 0x00000700;     //BANKCON2
   p[4] = 0x00000700;     //BANKCON3 
   p[5] = 0x00000700;     //BANKCON4
   p[6] = 0x00000700;     //BANKCON5
   p[7] = 0x00018005;     //BANKCON6
   p[8] = 0x00018005;     //BANKCON7
   
   
   p[9]  = 0x008C04F4;
   p[10 ] = 0x000000B1;     //BANKSIZE
   p[11] = 0x00000030;     //MRSRB6
   p[12] = 0x00000030;     //MRSRB7
}

void copy_steppingstone_to_sdram(void)
{
   unsigned int *pdwSrc  = (unsigned int *)0;
   unsigned int *pdwDest = (unsigned int *)0x30000000;
   
   while (pdwSrc < (unsigned int *)4096)
   {
       *pdwDest = *pdwSrc;
       pdwDest++;
       pdwSrc++;
   }
}

#define GPB5_out        (1<<(5*2))      // LED1
#define GPB6_out        (1<<(6*2))      // LED2
#define GPB7_out        (1<<(7*2))      // LED3
#define GPB8_out        (1<<(8*2))      // LED4

#define GPG11_eint      (2<<(11*2))     // K1,EINT19
#define GPG3_eint       (2<<(3*2))      // K2,EINT11
#define GPF3_eint       (2<<(3*2))      / / K3,EINT3
#define GPF2_eint       (2<<(2*2))      // K4,EINT2
 
void init_led(void)
{
   GPBCON = GPB5_out | GPB6_out | GPB7_out | GPB8_out;
}

void timer0_init(void)
{
   TCFG0  = 99;        // Prescaler 0 = 99        
   TCFG1  = 0x03;      // Select 16-division
   TCNTB0 = 31250;     // Trigger an interrupt every 0.5 seconds
   TCON   |= (1<<1);   // Manual update
   TCON   = 0x09;      // Automatically load, clear the "manual update" bit, and start timer 0
}

void init_irq(void)
{        
   // Timer 0 interrupt enable
   INTMSK   &= (~(1<<10));
}

#include "s3c24xx.h"

void Timer0_Handle(void)
{
   
   if(INTOFFSET == 10)
   {
       GPBDAT = ~(GPBDAT & (0xf << 5));
   }
   //Clear interrupt
   SRCPND = 1 << INTOFFSET;
   INTPND = INTPND;     
}

int main(void)
{
   while(1);
   return 0;
}