#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);
   }
}