121 lines
5.4 KiB
C
121 lines
5.4 KiB
C
/*****************************************************************************/
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/* */
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/* peripherals.h */
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/* */
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/* Memory-mapped peripheral subsystem for the 6502 simulator */
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/* */
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/* */
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/* */
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/* (C) 2024-2025, Sidney Cadot */
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/* */
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/* */
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/* This software is provided 'as-is', without any expressed or implied */
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/* warranty. In no event will the authors be held liable for any damages */
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/* arising from the use of this software. */
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/* */
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/* Permission is granted to anyone to use this software for any purpose, */
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/* including commercial applications, and to alter it and redistribute it */
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/* freely, subject to the following restrictions: */
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/* */
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/* 1. The origin of this software must not be misrepresented; you must not */
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/* claim that you wrote the original software. If you use this software */
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/* in a product, an acknowledgment in the product documentation would be */
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/* appreciated but is not required. */
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/* 2. Altered source versions must be plainly marked as such, and must not */
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/* be misrepresented as being the original software. */
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/* 3. This notice may not be removed or altered from any source */
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/* distribution. */
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/* */
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/*****************************************************************************/
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#ifndef PERIPHERALS_H
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#define PERIPHERALS_H
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#include <stdint.h>
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/* The memory range where the memory-mapped peripherals can be accessed. */
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#define PERIPHERALS_APERTURE_BASE_ADDRESS 0xffc0
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#define PERIPHERALS_APERTURE_LAST_ADDRESS 0xffc9
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/* Declarations for the COUNTER peripheral (currently the only peripheral). */
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#define PERIPHERALS_COUNTER_ADDRESS_OFFSET_LATCH 0x00
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#define PERIPHERALS_COUNTER_ADDRESS_OFFSET_SELECT 0x01
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#define PERIPHERALS_COUNTER_ADDRESS_OFFSET_VALUE 0x02
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#define PERIPHERALS_COUNTER_LATCH (PERIPHERALS_APERTURE_BASE_ADDRESS + PERIPHERALS_ADDRESS_OFFSET_COUNTER_LATCH)
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#define PERIPHERALS_COUNTER_SELECT (PERIPHERALS_APERTURE_BASE_ADDRESS + PERIPHERALS_ADDRESS_OFFSET_COUNTER_SELECT)
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#define PERIPHERALS_COUNTER_VALUE (PERIPHERALS_APERTURE_BASE_ADDRESS + PERIPHERALS_ADDRESS_OFFSET_COUNTER)
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#define PERIPHERALS_COUNTER_SELECT_CLOCKCYCLE_COUNTER 0x00
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#define PERIPHERALS_COUNTER_SELECT_INSTRUCTION_COUNTER 0x01
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#define PERIPHERALS_COUNTER_SELECT_IRQ_COUNTER 0x02
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#define PERIPHERALS_COUNTER_SELECT_NMI_COUNTER 0x03
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#define PERIPHERALS_COUNTER_SELECT_WALLCLOCK_TIME 0x80
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#define PERIPHERALS_COUNTER_SELECT_WALLCLOCK_TIME_SPLIT 0x81
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typedef struct {
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/* The invisible counters that keep processor state. */
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uint64_t ClockCycles;
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uint64_t CpuInstructions;
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uint64_t IrqEvents;
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uint64_t NmiEvents;
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/* The 'latched_...' fields below hold values that are sampled upon a write
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* to the PERIPHERALS_COUNTER_LATCH address.
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* One of these will be visible (read only) through an eight-byte aperture.
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* The purpose of these latched registers is to read 64-bit values one byte
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* at a time, without having to worry that their content will change along
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* the way.
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*/
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uint64_t LatchedClockCycles;
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uint64_t LatchedCpuInstructions;
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uint64_t LatchedIrqEvents;
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uint64_t LatchedNmiEvents;
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uint64_t LatchedWallclockTime;
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uint64_t LatchedWallclockTimeSplit;
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/* Select which of the six latched registers will be visible.
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* This is a single byte, read/write register, accessible via address
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* PERIPHERALS_COUNTER_SELECT. If a non-existent latch register is selected,
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* the PERIPHERALS_COUNTER_VALUE will be zero.
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*/
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uint8_t LatchedValueSelected;
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} CounterPeripheral;
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/* Declare the 'Sim65Peripherals' type and its single instance 'Peripherals'. */
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typedef struct {
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/* State of the peripherals available in sim65.
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* Currently, there is only one peripheral: the Counter. */
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CounterPeripheral Counter;
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} Sim65Peripherals;
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extern Sim65Peripherals Peripherals;
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/*****************************************************************************/
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/* Code */
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/*****************************************************************************/
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void PeripheralsWriteByte (uint8_t Addr, uint8_t Val);
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/* Write a byte to a memory location in the peripheral address aperture. */
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uint8_t PeripheralsReadByte (uint8_t Addr);
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/* Read a byte from a memory location in the peripheral address aperture. */
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void PeripheralsInit (void);
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/* Initialize the peripherals. */
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/* End of peripherals.h */
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#endif
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