Implementation of timer to milliseconds conversion using lookup tables. More...

#include <timer_ms_to_ticks_table.h>
#include <frequency.h>
#include <interrupt.h>

Include dependency graph for timer_ms_to_ticks_table.c:

Functions
void	timer0_1ms_delay_init ()
	Initializes Timer0 for 1 millisecond delay using precalculated ticks.

void	timer0_1ms_delay ()
	Executes a 1 millisecond delay using Timer0.

Variables
uint16_t	precalc_1t_ticks [8]
	Precalculated timer ticks for 1ms delay in 1T mode.

uint16_t	precalc_12t_ticks [8]
	Precalculated timer ticks for 1ms delay in 12T mode.

Detailed Description

Implementation of timer to milliseconds conversion using lookup tables.

This file provides the implementation for fast millisecond to tick conversion using precalculated lookup tables. The tables contain precomputed values for 1 millisecond delays at various system clock frequencies and divider settings.

Lookup table organization:

precalc_1t_ticks: Values for 1T mode (1 clock cycle per tick)
precalc_12t_ticks: Values for 12T mode (12 clock cycles per tick)

Each array has 8 elements, with the index corresponding to the frequency scale divider (from CLK_DIV register bits [0..2]). The frequency scale ranges from 0 to 7, corresponding to clock dividers of 1, 2, 4, 8, 16, 32, 64, and 128.

The precalculated values are derived from the formula: ticks = (SYSclk / divider) * 0.001

Where SYSclk = MAIN_Fosc / (2^divider_scale)

Example calculations for 11,059,200 Hz crystal:

1T mode, divider_scale=0 (SYSclk=11,059,200 Hz): ticks = 11059
12T mode, divider_scale=0 (SYSclk=11,059,200 Hz): ticks = 922

Note: The values in the tables are rounded approximations. The actual values in comments show the exact mathematical results.; The timer_ms_to_ticks_table.h header provides the public API for accessing these lookup tables via the timer_1ms_to_ticks() function.

See also: timer_ms_to_ticks_table.h - Public API for table-based conversion; timer_to_ms_common.h - Dynamic conversion functions; frequency.h - System clock frequency management

Author: Michael Golovanov

Function Documentation

◆ timer0_1ms_delay()

void timer0_1ms_delay ( )

Executes a 1 millisecond delay using Timer0.

Starts Timer0 and waits for the overflow flag (TF0) to be set, indicating that the configured 1ms time interval has elapsed. The timer is configured by timer0_1ms_delay_init() with the appropriate reload values for the system clock frequency.

Note: This is a blocking function that waits in a polling loop until the timer overflow occurs.; Timer0 must be initialized with timer0_1ms_delay_init() before calling this function.

See also: timer0_1ms_delay_init() - Initializes Timer0 for 1ms delay; TF0 - Timer0 overflow flag; TR0 - Timer0 run control bit

◆ timer0_1ms_delay_init()

void timer0_1ms_delay_init ( )

Initializes Timer0 for 1 millisecond delay using precalculated ticks.

Note: Must be called before using timer0_1ms_delay() to ensure correct timer configuration for the current system clock settings.; Disables Timer0 interrupt during initialization to prevent unwanted interrupt service routine execution.

See also: get_frequency_divider_scale() - Gets current frequency scale index; get_timer0_clock_divider() - Gets Timer0 clock divider setting; timer0_1ms_delay() - Performs the actual 1ms delay; precalc_1t_ticks - Lookup table for 1T mode tick values; precalc_12t_ticks - Lookup table for 12T mode tick values

Variable Documentation

◆ precalc_12t_ticks

uint16_t precalc_12t_ticks[8]

Initial value:

Precalculated timer ticks for 1ms delay in 12T mode.

Array index corresponds to frequency scale divider (CLK_DIV bits [0..2])

These values represent the number of timer ticks required for a 1 millisecond delay when the timer is configured in 12T mode (twelve clock cycles per tick). The array index is determined by the system clock frequency scale setting.

Index mapping:

Index 0: divider_scale=0, SYSclk = MAIN_Fosc, divider=12
Index 1: divider_scale=1, SYSclk = MAIN_Fosc/2, divider=24
Index 2: divider_scale=2, SYSclk = MAIN_Fosc/4, divider=48
Index 3: divider_scale=3, SYSclk = MAIN_Fosc/8, divider=96
Index 4: divider_scale=4, SYSclk = MAIN_Fosc/16, divider=192
Index 5: divider_scale=5, SYSclk = MAIN_Fosc/32, divider=384
Index 6: divider_scale=6, SYSclk = MAIN_Fosc/64, divider=768
Index 7: divider_scale=7, SYSclk = MAIN_Fosc/128, divider=1536

Note: Values in comments show exact mathematical calculations

See also: get_frequency_divider_scale() - Function to get current index; timer_1ms_to_ticks() - Function using this table

◆ precalc_1t_ticks

uint16_t precalc_1t_ticks[8]