1. guide

1.1 Purpose

This library mainly provides function-like macros to obtain programmable WAIT and processing times.

1.2 Overview

The timer uses the free running timer (FRT) in the CPU and the timer interrupt in the SCU. We have prepared function-like macros considering the following uses for each device.

●SCU

• You can obtain time synchronized with V-Blank and H-Blank. It can be used as information for creating game screen effects.

●CPU

• You can set the exact wait time (WAIT) required during programming. You can perform a relatively accurate WAIT within a C language program.

• You can get the elapsed time. It can be used to measure program processing time.

1.3 Detailed explanation

●SCU

＜ how to use＞

For details on how to use it, see timer interrupt in the SCU user's manual.

＜ calling sequence＞

The following is a calling sequence that uses timer 1 to generate a timer 1 interrupt when drawing the 10th bit of each line, and inverts that line if it is an odd numbered line.

Uint32 time_flg; /* Interrupt flag */
...
void vblankOut() /* V-BLANK OUT execution function */
{
     Uint32 intr_count = 0; /* Interrupt counter */
     ...
     TIM_T1_DISABLE(); /* Disable timer 1 interrupt */
     TIM_T1_SET_MODE(TIM_MD_LINE); /* Specify interrupt generation every line */
     TIM_T1_SET_DATA(10);                 
                  /* Specify the interrupt generation timing at the 10th bit of the line */
     time_flg = OFF; /* Turn off interrupt flag */
     TIM_T1_ENABLE(); /* Timer 1 interrupt enable */
     ...
     for(intr_count< ALL_LINE_NUM){
                                           /* Until all line interrupts are executed */
               changeLine(intr_count); /* Invert odd line */
               intr_count ++; /* Line count */
     }
}
void timeIntr() /* Interrupt execution function */
{
     time_flg = ON; /* Turn on interrupt flag */
}

●CPU

＜ Basics＞

counter value

A counter value is used to specify time to FRT. This counter value is explained below.

The count-up period of the counter value changes depending on the division specification and graphic mode specification. The count-up period can be calculated using the following calculation.

Count-up period (s) = Divide x 1/Clock frequency (Hz)

It is convenient to use the following function-like macros to convert count values to microseconds and microseconds to count values.

function	function-like macro	number
Counter value -＞ microsecond conversion	TIM_FRT_CNT_TO_MCR	15
microsecond -＞ Counter value conversion	TIM_FRT_MCR_TO_CNT	16

＜ how to use＞

Initialization

Execute the following function-like macro before obtaining the elapsed time and using the wait time (WAIT) function.

function	function-like macro	number
FRT initialization	TIM_FRT_INIT	8

How to obtain elapsed time

The following functions are provided to obtain the elapsed time.

function	function-like macro	number
Counter value setting (16 bits)	TIM_FRT_SET_16	9
Obtain counter value (16 bit)	TIM_FRT_GET_16	10

void sysInit()
{
     TIM_FRT_INIT(8); /* Set divider to 8 */
     ...
}

 void writeFrameBuff()
{
     Uint16 count; /* Obtained count value storage area */
     float micro_sec; /* Microsecond storage area */
     TIM_FRT_SET_16(0); /* Set the count value to 0 */
     WriteAllVram(); /* Execute the process you want to measure */
     count = TIM_Frt_Get_16(); /* Get the count value */
                                           /* count indicates the execution time of WriteAllVram() */
     micro_sec = TIM_FRT_CNT_TO_MCR(count);/* Convert counter value to microseconds */
     printDisplay(micro_sec); /* Display the elapsed time on the screen */
}