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mcs48: EA line / MB8884

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* MB8884 is a I8035 ==> 12 addr, no internal rom map
* EA line high: external access - this is "default"

The whole EA implementation is as Aaron named it, cheeky. EA=1 external rom access, EA=0 internal rom access.
But all variants are treated the same, i.e. for i8035, MB8884, I8039, the external rom is used in the same
way as the internal.
This commit is contained in:
Couriersud 2008-08-30 00:36:56 +00:00
parent 322e67afbb
commit 7d6a80c480
1 changed files with 13 additions and 4 deletions
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17
src/emu/cpu/mcs48/mcs48.c
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@ -196,7 +196,7 @@ static void check_irqs(void);
INLINE UINT8 opcode_fetch(offs_t address)
{
/* fix me - need to figure out how to bypass internal ROM in this case */
if (mcs48.ea && address < mcs48.int_rom_size)
if (!mcs48.ea && address < mcs48.int_rom_size)
return 0x00;
return cpu_readop(address);
}
@ -210,7 +210,7 @@ INLINE UINT8 opcode_fetch(offs_t address)
INLINE UINT8 argument_fetch(offs_t address)
{
/* fix me - need to figure out how to bypass internal ROM in this case */
if (mcs48.ea && address < mcs48.int_rom_size)
if (!mcs48.ea && address < mcs48.int_rom_size)
return 0x00;
return cpu_readop_arg(address);
}
@ -706,6 +706,14 @@ static void mcs48_init(int index, int clock, const void *config, int (*irqcallba
{
memset(&mcs48, 0, sizeof(mcs48));
/* External access line
* EA=1 : read from external rom
* EA=0 : read from internal rom
*/
/* FIXME: Current implementation suboptimal */
mcs48.ea = 1;
mcs48.irq_callback = irqcallback;
mcs48.int_rom_size = romsize;
@ -923,6 +931,7 @@ static int mcs48_execute(int cycles)
ADDRESS MAPS
***************************************************************************/
/* FIXME: the memory maps should probably support rom banking for EA */
static ADDRESS_MAP_START(program_10bit, ADDRESS_SPACE_PROGRAM, 8)
AM_RANGE(0x00, 0x3ff) AM_ROM
ADDRESS_MAP_END
@ -1202,9 +1211,8 @@ void mb8884_get_info(UINT32 state, cpuinfo *info)
{
switch (state)
{
case CPUINFO_INT_ADDRBUS_WIDTH + ADDRESS_SPACE_PROGRAM: info->i = 10; break;
case CPUINFO_INT_ADDRBUS_WIDTH + ADDRESS_SPACE_PROGRAM: info->i = 12; break;
case CPUINFO_INT_ADDRBUS_WIDTH + ADDRESS_SPACE_DATA: info->i = 6; break;
case CPUINFO_PTR_INTERNAL_MEMORY_MAP + ADDRESS_SPACE_PROGRAM: info->internal_map8 = address_map_program_10bit; break;
case CPUINFO_PTR_INTERNAL_MEMORY_MAP + ADDRESS_SPACE_DATA: info->internal_map8 = address_map_data_6bit; break;
case CPUINFO_PTR_INIT: info->init = i8035_init; break;
case CPUINFO_STR_NAME: strcpy(info->s, "MB8884"); break;
@ -1285,6 +1293,7 @@ void m58715_get_info(UINT32 state, cpuinfo *info)
{
case CPUINFO_INT_ADDRBUS_WIDTH + ADDRESS_SPACE_PROGRAM: info->i = 12; break;
case CPUINFO_INT_ADDRBUS_WIDTH + ADDRESS_SPACE_DATA: info->i = 7; break;
case CPUINFO_PTR_INTERNAL_MEMORY_MAP + ADDRESS_SPACE_PROGRAM: info->internal_map8 = address_map_program_11bit; break;
case CPUINFO_PTR_INTERNAL_MEMORY_MAP + ADDRESS_SPACE_DATA: info->internal_map8 = address_map_data_7bit; break;
case CPUINFO_PTR_INIT: info->init = i8039_init; break;
case CPUINFO_STR_NAME: strcpy(info->s, "M58715"); break;