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Merge pull request #2593 from sidneycadot/sim65-add-peripheral-support-and-docs-and-samples

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sim65: add C/assembly support, docs, and samples for the new peripheral functionality.
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Sidney Cadot
2025-01-11 08:50:28 +01:00
committed by GitHub
parent b05bb4a44f aacd64b2bc
commit 9fd090ae8b
8 changed files with 603 additions and 16 deletions
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/*****************************************************************************/
/* */
/* sim65.h */
/* */
/* Definitions for the sim6502 and sim65c02 targets */
/* */
/* */
/* */
/* (C) 2025 Sidney Cadot */
/* */
/* */
/* This software is provided 'as-is', without any expressed or implied */
/* warranty. In no event will the authors be held liable for any damages */
/* arising from the use of this software. */
/* */
/* Permission is granted to anyone to use this software for any purpose, */
/* including commercial applications, and to alter it and redistribute it */
/* freely, subject to the following restrictions: */
/* */
/* 1. The origin of this software must not be misrepresented; you must not */
/* claim that you wrote the original software. If you use this software */
/* in a product, an acknowledgment in the product documentation would be */
/* appreciated but is not required. */
/* 2. Altered source versions must be plainly marked as such, and must not */
/* be misrepresented as being the original software. */
/* 3. This notice may not be removed or altered from any source */
/* distribution. */
/* */
/*****************************************************************************/
#ifndef _SIM65_H
#define _SIM65_H
/* Check that we include this file while compiling to a compatible target. */
#if !defined(__SIM6502__) && !defined(__SIM65C02__)
# error This module may only be used when compiling for the sim6502 or sim65c02 targets!
#endif
#include <stdint.h>
/* The sim65 targets (sim6502, sim65c02) have a peripheral memory aperture located at
* address range 0xFFC0 .. 0xFFDF. Currently, the following peripherals are located
* inside that memory apeture:
*
* $FFC0 .. $FFC9 "counter" peripheral
* $FFCA .. $FFCB "sim65 control" peripheral
* $FFCC .. $FFDF (currently unused)
*
* The "peripherals" structure below corresponds to the register layout of the currently
* defined peripherals in this memory range. Combined with the fact that the sim6502 and
* sim65c02 linker configuration files define the "peripherals" symbol to be fixed at
* address $FFC0, this provides easy-to-use and efficient access to the peripheral registers.
*
* After including "sim65.h", it is possible for a C program to do things like:
*
* {
* peripherals.counter.latch = 0;
* peripherals.sim65.cpu_mode = SIM65_CPU_MODE_6502X;
* peripherals.sim65.trace_mode = SIM65_TRACE_MODE_ENABLE_FULL;
* }
*
* Note that "peripherals" variable is declared volatile. This instructs a C compiler to
* forego optimizations on memory accesses to the variable. However, CC65 currently ignores
* the volatile attribute. Fortunately, it is not smart with respect to optimizing
* memory accesses, so accessing the "peripherals" fields works fine in practice.
*/
extern volatile struct {
struct {
uint8_t latch;
uint8_t select;
union {
uint8_t value [8]; /* Access value as eight separate bytes. */
uint16_t value16 [4]; /* Access value as four 16-bit words. */
uint32_t value32 [2]; /* Access value as two 32-bit long words. */
};
} counter;
struct {
uint8_t cpu_mode;
uint8_t trace_mode;
} sim65;
} peripherals;
/* Values for the peripherals.counter.select field. */
#define COUNTER_SELECT_CLOCKCYCLE_COUNTER 0x00
#define COUNTER_SELECT_INSTRUCTION_COUNTER 0x01
#define COUNTER_SELECT_IRQ_COUNTER 0x02
#define COUNTER_SELECT_NMI_COUNTER 0x03
#define COUNTER_SELECT_WALLCLOCK_TIME 0x80
#define COUNTER_SELECT_WALLCLOCK_TIME_SPLIT 0x81
/* Values for the peripherals.sim65.cpu_mode field. */
#define SIM65_CPU_MODE_6502 0x00
#define SIM65_CPU_MODE_65C02 0x01
#define SIM65_CPU_MODE_6502X 0x02
/* Bitfield values for the peripherals.sim65.trace_mode field. */
#define SIM65_TRACE_MODE_FIELD_INSTR_COUNTER 0x40
#define SIM65_TRACE_MODE_FIELD_CLOCK_COUNTER 0x20
#define SIM65_TRACE_MODE_FIELD_PC 0x10
#define SIM65_TRACE_MODE_FIELD_INSTR_BYTES 0x08
#define SIM65_TRACE_MODE_FIELD_INSTR_ASSEMBLY 0x04
#define SIM65_TRACE_MODE_FIELD_CPU_REGISTERS 0x02
#define SIM65_TRACE_MODE_FIELD_CC65_SP 0x01
/* Values for the peripherals.sim65.trace_mode field that fully disable / enable tracing. */
#define SIM65_TRACE_MODE_DISABLE 0x00
#define SIM65_TRACE_MODE_ENABLE_FULL 0x7F
/* Convenience macros to enable / disable tracing at runtime. */
#define TRACE_ON() do peripherals.sim65.trace_mode = SIM65_TRACE_MODE_ENABLE_FULL; while(0)
#define TRACE_OFF() do peripherals.sim65.trace_mode = SIM65_TRACE_MODE_DISABLE; while(0)
/* Convenience macro to query the CPU mode at runtime. */
#define GET_CPU_MODE() peripherals.sim65.cpu_mode
/* Convenience macro to set the CPU mode at runtime.
*
* Use SIM65_CPU_MODE_6502, SIM65_CPU_MODE_65C02, or SIM65_CPU_MODE_6502 as argument.
*
* Important Note:
*
* When running in a program compiled for the "sim6502" target, it is safe to switch to
* 65C02 or 6502X mode, since the runtime library will only use plain 6502 opcodes, and
* those work the same in 65C02 and 6502X mode.
*
* However, when running in a program compiled for the "sim65c02" target, it is NOT safe
* to switch to 6502 or 6502X mode, since many routines in the runtime library use
* 65C02-specific opcodes, and these will not work as expected when the CPU is switched
* to 6502 or 6502X mode. When such an instruction is encountered, the program will
* exhibit undefined behavior.
*/
#define SET_CPU_MODE(mode) do peripherals.sim65.cpu_mode = mode; while(0)
/* End of sim65.h */
#endif