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https://github.com/hsoft/collapseos.git
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55 lines
1.5 KiB
C
55 lines
1.5 KiB
C
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#include <string.h>
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#include "at28.h"
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void at28_init(AT28 *at28, Z80Context *cpu, ushort startoffset, ushort size)
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{
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at28->cpu = cpu;
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memset(at28->mem, 0, LEN16BIT);
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at28->startoffset = startoffset;
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at28->size = size;
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at28->wrstamp = 0;
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}
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static void _maybe_end_write(AT28 *at28)
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{
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unsigned int ts = at28->cpu->tstates;
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unsigned int stamp = at28->wrstamp;
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// if ts < stamp, it means that the CPU re-initialized its counter
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if (stamp && ((ts < stamp) || (ts > stamp+80000))) {
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at28->mem[at28->wraddr] = at28->wrval;
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at28->wrstamp = 0;
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}
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}
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byte at28_mem_read(AT28 *at28, ushort addr)
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{
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_maybe_end_write(at28);
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if ((addr >= at28->startoffset) && (addr < at28->startoffset+at28->size)) {
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if (at28->wrstamp) {
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if (addr == at28->wraddr) {
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// poll
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at28->pollval ^= 0b01000000; // bit 6 toggle
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return at28->pollval;
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} else {
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// reading another addr interrupts write
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at28->wrstamp = 0;
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}
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}
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return at28->mem[addr];
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} else {
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return emul_mem_read(0, addr);
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}
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}
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void at28_mem_write(AT28 *at28, ushort addr, byte val)
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{
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_maybe_end_write(at28);
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if ((addr >= at28->startoffset) && (addr < at28->startoffset+at28->size)) {
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at28->wrstamp = at28->cpu->tstates;
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at28->wraddr = addr;
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at28->wrval = at28->pollval = val;
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} else {
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emul_mem_write(0, addr, val);
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}
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}
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