scemu/mem.c

#include <u.h>
#include <libc.h>
#include "dat.h"
#include "fns.h"

u8int	*mem;
u8int	*romptr;

u8int
memread(u16int a)
{
	return mem[a];
}

void
memwrite(u16int a, u8int v)
{
	if((void*)a < romptr)
		mem[a] = v;
}


void
push8(u8int v)
{
	memwrite(0x100 | rS--, v);
}

void
push16(u16int v)
{
	memwrite(0x100 | rS--, v >> 8);
	memwrite(0x100 | rS--, v);
}

u8int
pop8(void)
{
	return memread(0x100 | ++rS);
}

u16int
pop16(void)
{
	u16int v;
	
	v = memread(0x100 | ++rS);
	v |= memread(0x100 | ++rS) << 8;
	return v;
}

u8int
fetch8(void)
{
	return memread(pc++);
}

u16int
fetch16(void)
{
	u16int r;
	
	r = memread(pc++);
	r |= memread(pc++) << 8;
	return r;
}