mapper_xram_single.h

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// Copyright 2022 LLVM-MOS Project
// Licensed under the Apache License, Version 2.0 with LLVM Exceptions.
// See https://github.com/llvm-mos/llvm-mos-sdk/blob/main/LICENSE for license
// information.
 
// Functions for single-area RAM bank switching schemes.
// (3E, E7)
 
#ifndef _MAPPER_XRAM_H_
#define _MAPPER_XRAM_H_
 
#include <mapper.h>
 
#ifdef __cplusplus
extern "C" {
#endif
 
// RAM bank index type.
typedef unsigned char ram_bank_t;
 
// Macro to declare a variable in XRAM.
// - index = XRAM bank index
// - declaration = variable declaration
// This will declare two variables, one read-only and one write-only.
// For example, DECLARE_XRAM_VARIABLE(0, int my_var)
// creates two variables: my_var_read and my_var_write.
// NOTE: These variables are not initialized by default.
#define _DECLARE_XRAM_VARIABLE(index, declaration) \
    __attribute__((section(".xram" #index "_read"))) volatile const declaration##_read; \
    __attribute__((section(".xram" #index "_write"))) volatile declaration##_write;
 
#define DECLARE_XRAM_VARIABLE(index, declaration) _DECLARE_XRAM_VARIABLE(index, declaration)
 
// Switch in a RAM bank.
void ram_select(ram_bank_t bank_id);
 
// Switch to another RAM bank and call this function.
__attribute__((callback(2))) void banked_call_ram(ram_bank_t bank_id,
                                                  void (*method)(void));
 
// Write a byte to extended RAM at set offset
// RAM must be selected first, or use banked_call_ram
void xram_write(int offset, unsigned char value);
 
// Read a byte from extended RAM at set offset
// RAM must be selected first, or use banked_call_ram
unsigned char xram_read(int offset);
 
#ifdef __cplusplus
}
#endif
 
#endif // _MAPPER_H_