The correct use of S3C2440A timer

The S3C2440A has five 16-bit timers. Timers 0, 1, 2, and 3 have pulse width modulation (PWM) capabilities. Timer 4 is an internal timer with no output pins. Timer 0 also contains a dead zone generator for high current drive

Timers 0 and 1 share one 8-bit prescaler, and Timers 2, 3, and 4 share another 8-bit prescaler. Each timer has a clock divider that can generate 5 different divided signals (1/2, 1/4, 1/8, 1/16 and TCLK). Each timer module gets its own clock signal from the clock divider that gets the clock from the corresponding 8-bit prescaler. The 8-bit prescaler is programmable and divides PCLK by the load value stored in the TCFG0 and TCFG1 registers.

Each timer has its own 16-bit down counter driven by the timer clock. When the down counter reaches zero, a timer interrupt request is generated to notify the CPU that the timer operation has completed. When the timer counter reaches zero, the corresponding TCNTBn value will be automatically loaded into the down counter to continue the next operation.

There are two modes for using the timer. The first is normal timing and the second is PWM output.

Let's talk about ordinary timing first. The general use process of a timer will include these steps

1. Enable the corresponding timer peripheral in the low-power register

2. Set the clock division ratio to obtain the timer's count clock

3. Set the timer value (reload value), configure the middle end, and start the timer

4. Wait for the interrupt to occur and clear the interrupt in the interrupt handling function

Based on these steps, we need to pay attention to the following registers

First, set the division ratio of PCLK to timer. There are two clocks, 01 timer and 234 timer.

Then the second frequency division

You can choose 1/2%201/4%201/8%201/16 clocks. The clock source is divided from the previous register.

Set the timer to automatically reload and start the timer. Note that in this register, you must clear it again after manually updating it, otherwise the timer will not run.

I've encountered this problem before

Set the timer auto-reload value

Then set the interrupt according to the previous interrupt setting method. The timer has no secondary source. Take time0 as an example

1. Source hangs srcpend

2. Interrupt mode intmode

3. Interrupt mask intmask

4. Interrupt suspend intpend

After enabling the interrupt, the timer can be used normally

The specific code is as follows:

TImer.c

#include "TImer.h" u8TImer0Up = 0; void __irqTImer0() { rSRCPND " = (1 < < 10); // Clear source pending rINTPND | = (1 < < 10); // Clear interrupt pending timer0Up = 1; } // Timer initialization // prescaler8 is the divider value, 0-255 // mux timer's strobe input 01/211/421/831/16 // Timer reload value void InitTimer0 (u8prescaler, u8mux, u16count) { rCLKCON | = (1 < < 8); // Turn on timer clock rTCFG0 & = ~ 0xff; // Clear divider rTCFG0 | = prescaler; // Set prescaler rTCFG1 & = ~ (0x0f < < 0); rT CFG1|=(mux<<0);//Set the strobe input//Set the count value of the timer rTCMPB0=0x0; rTCNTB0=count;//Set the initial value//Start the timer rTCON|=(1<<1);//Update TCNTB0 and TCMPB0 rTCON|=(1<<3);//Start automatic reload rTCON&=~(1<<1);//Clear manual update rSRCPND|=(1<<10);//Clear source pending rINTPND|=(1<<10);//Clear interrupt pending rINTMOD&=~(1<<10);//Set the interrupt mode to IRQ mode rINTMSK&=~(1<<10);//Enable timer interrupt pISR_TIMER0=(unsigned)timer0;//Set interrupt address rTCON|=(1<<0);//Start timer 0 }

Timer.h

#ifndef__TIMER_H #define__TIMER_H #include "2440addr.h" #include "led.h" #include "uart0.h" externu8timer0Up; void InitTimer0(u8prescaler, u8mux, u16count); #endif

There are several other registers that need attention when outputting PWM waveforms.

First: PWM output does not need to enable interrupt, but the corresponding pin multiplexing function must be set to PWM function, as shown in the figure, TCLK

Second, to use the pwm function, the compare register must be enabled, that is

Third, see if you need to reverse according to your needs. What is reverse?

It’s TCNT

Pwm.c

#include "pwm.h" //compare the value of the compare register voidTimer0PwmInit (u8prescaler, u8mux, u16count, u16compare) {rGPBCON&=~3;rGPBCON"=2;//Set GPB0 to OUT0rGPBUP=0x0;//Enable pull-up rCLKCON|=(1<<8);//Turn on the timer clock rTCFG0&=~0xff;//Clear the divider rTCFG0|=prescaler;//Set the prescaler rTCFG1&=~(0x0f<<0);rTCFG1|=(mux<<0);//Set the strobe input //Set the count value of the timer rTCMPB0=compare;//compare register value rTCNTB0=count;//set initial value//start timer rTCON|=(1<<1);//update TCNTB0 and TCMPB0 rTCON|=(1<<3);//start automatic reload rTCON&=~(1<<1);//clear manual update rTCON|=(1<<0);//start timer 0 }

Pwm.h

#ifndef__PWM_H_ #define__PWM_H_ #include "2440addr.h" #include "def.h" //compare the value of the compare register voidTomer0PwmInit (u8prescaler, u8mux, u16count, u16compare); #endif