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lxdream.org :: lxdream/test/timer.c
lxdream 0.9.1
released Jun 29
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filename test/timer.c
changeset 262:bc96e0b79308
prev225:e5cea6125580
next272:fb6be85235e8
author nkeynes
date Wed Jan 03 09:03:50 2007 +0000 (13 years ago)
permissions -rw-r--r--
last change Fix to actually work (need the write read/write sizes)
Implement the microsecond conversion function
file annotate diff log raw
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#include "../lib.h"
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#define TMU_CHANNEL 2
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#define BASE_TICKS_PER_US 200
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#define CLOCK_DIVIDER 16
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#define TOCR 0xFFD80000  /* Output control register */
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#define TSTR 0xFFD80004  /* Start register */
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#define TCOR(c) (0xFFD80008 + (c*12))  /* Constant register */
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#define TCNT(c) (0xFFD8000C + (c*12))  /* Count register */
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#define TCR(c)  (0xFFD80010 + (c*12))  /* Control register */
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/**
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 * Initialize the on-chip timer controller. We snag TMU channel 2 in its
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 * highest resolution mode, and start it counting down from max_int. 
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 */
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void timer_start() {
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    unsigned int val = byte_read(TSTR);
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    byte_write( TSTR, val & (~(1<<TMU_CHANNEL)) ); /* Stop counter */
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    long_write( TCOR(TMU_CHANNEL), 0xFFFFFFFF );
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    long_write( TCNT(TMU_CHANNEL), 0xFFFFFFFF );
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    word_write( TCR(TMU_CHANNEL), 0x00000000 );
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    byte_write( TSTR, val | (1<<TMU_CHANNEL) );
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}
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/**
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 * Report the current value of TMU2.
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 */
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unsigned int timer_gettime() {
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    return long_read(TCNT(TMU_CHANNEL));
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}
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/**
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 * Stop TMU2 and report the current value.
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 */
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unsigned int timer_stop() {
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    long_write( TSTR, long_read(TSTR) & (~(1<<TMU_CHANNEL)) );
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    return long_read( TCNT(TMU_CHANNEL) );
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}
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/**
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 * Convert the supplied timer value to a number of micro seconds since the timer
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 * was started.
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 */
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unsigned int timer_to_microsecs( unsigned int value ) {
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    return (0xFFFFFFFF - value) * CLOCK_DIVIDER / BASE_TICKS_PER_US;
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}
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unsigned int timer_gettime_us() {
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    return timer_to_microsecs( timer_gettime() );
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}
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