mirror of
https://github.com/hsoft/collapseos.git
synced 2024-11-14 17:58:06 +11:00
953e040231
This will facilitate the development of a solution for cross-compiling directly to EEPROM.
55 lines
1.5 KiB
C
55 lines
1.5 KiB
C
#include <string.h>
|
|
#include "at28.h"
|
|
|
|
void at28_init(AT28 *at28, Z80Context *cpu, ushort startoffset, ushort size)
|
|
{
|
|
at28->cpu = cpu;
|
|
memset(at28->mem, 0, LEN16BIT);
|
|
at28->startoffset = startoffset;
|
|
at28->size = size;
|
|
at28->wrstamp = 0;
|
|
}
|
|
|
|
static void _maybe_end_write(AT28 *at28)
|
|
{
|
|
unsigned int ts = at28->cpu->tstates;
|
|
unsigned int stamp = at28->wrstamp;
|
|
// if ts < stamp, it means that the CPU re-initialized its counter
|
|
if (stamp && ((ts < stamp) || (ts > stamp+80000))) {
|
|
at28->mem[at28->wraddr] = at28->wrval;
|
|
at28->wrstamp = 0;
|
|
}
|
|
}
|
|
|
|
byte at28_mem_read(AT28 *at28, ushort addr)
|
|
{
|
|
_maybe_end_write(at28);
|
|
if ((addr >= at28->startoffset) && (addr < at28->startoffset+at28->size)) {
|
|
if (at28->wrstamp) {
|
|
if (addr == at28->wraddr) {
|
|
// poll
|
|
at28->pollval ^= 0b01000000; // bit 6 toggle
|
|
return at28->pollval;
|
|
} else {
|
|
// reading another addr interrupts write
|
|
at28->wrstamp = 0;
|
|
}
|
|
}
|
|
return at28->mem[addr];
|
|
} else {
|
|
return emul_mem_read(0, addr);
|
|
}
|
|
}
|
|
|
|
void at28_mem_write(AT28 *at28, ushort addr, byte val)
|
|
{
|
|
_maybe_end_write(at28);
|
|
if ((addr >= at28->startoffset) && (addr < at28->startoffset+at28->size)) {
|
|
at28->wrstamp = at28->cpu->tstates;
|
|
at28->wraddr = addr;
|
|
at28->wrval = at28->pollval = val;
|
|
} else {
|
|
emul_mem_write(0, addr, val);
|
|
}
|
|
}
|