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/****************************************************************************
* arch/z80/src/z180/z180_timerisr.c
*
* Copyright (C) 2012 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <stdint.h>
#include <time.h>
#include <debug.h>
#include <arch/board/board.h>
#include "clock/clock.h"
#include "up_internal.h"
#include "chip.h"
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/* "The Z180 contains a two channel 16-bit Programmable Reload Timer. Each
* PRT channel contains a 16-bit down counter and a 16-bit reload register."
* Channel 0 is dedicated as the system timer.
*/
/* "The PRT input clock for both channels is equal to the system clock
* divided by 20."
*/
#define Z180_PRT_CLOCK (Z180_SYSCLOCK / 20)
/* The data Register "(TMDR) is decremented once every twenty clocks. When
* TMDR counts down to 0, it is automatically reloaded with the value
* contained in the Reload Register (RLDR)."
*/
#define A180_PRT0_RELOAD (Z180_PRT_CLOCK / CLK_TCK)
/****************************************************************************
* Private Types
****************************************************************************/
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
/****************************************************************************
* Global Functions
****************************************************************************/
/****************************************************************************
* Function: up_timerisr
*
* Description:
* The timer ISR will perform a variety of services for various portions
* of the systems.
*
****************************************************************************/
int up_timerisr(int irq, chipreg_t *regs)
{
/* "When TMDR0 decrements to 0, TIF0 is set to 1. This generates an interrupt
* request if enabled by TIE0 = 1. TIF0 is reset to 0 when TCR is read and
* the higher or lower byte of TMDR0 is read."
*/
(void)inp(Z180_PRT_TCR);
(void)inp(Z180_PRT0_DRL);
(void)inp(Z180_PRT0_DRH);
/* Process timer interrupt */
sched_process_timer();
return 0;
}
/****************************************************************************
* Function: up_timer_initialize
*
* Description:
* This function is called during start-up to initialize the timer
* interrupt.
*
****************************************************************************/
void up_timer_initialize(void)
{
uint8_t regval;
/* Configure PRT0 to interrupt at the requested rate */
/* First stop PRT0 and disable interrupts */
regval = inp(Z180_PRT_TCR);
regval &= (PRT_TCR_TIF0|PRT_TCR_TIE0|PRT_TCR_TDE0);
outp(Z180_PRT_TCR, regval);
/* Set the timer reload value so that the timer will interrupt at the
* desired frequency. "For writing, the TMDR down counting must be
* inhibited using the TDE (Timer Down Count Enable) bits in the TCR
* (Timer Control Register). Then, any or both higher and lower bytes of
* TMDR can be freely written (and read) in any order."
*/
outp(Z180_PRT0_RLDRL, (A180_PRT0_RELOAD & 0xff));
outp(Z180_PRT0_RLDRH, (A180_PRT0_RELOAD >> 8));
/* Enable down-counting */
regval |= PRT_TCR_TDE0;
outp(Z180_PRT_TCR, regval);
/* Attach the timer interrupt vector */
(void)irq_attach(Z180_PRT0, (xcpt_t)up_timerisr);
/* And enable the timer interrupt */
regval |= PRT_TCR_TIE0;
outp(Z180_PRT_TCR, regval);
}
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