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ti99: Extend gromemu cartridge type to support bank-switched ROMs.

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This commit is contained in:
Michael Zapf 2020-09-04 18:13:41 +02:00
parent 7bd9e6e6a6
commit 09ee11eabe
2 changed files with 40 additions and 13 deletions
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52
src/devices/bus/ti99/gromport/cartridges.cpp
View File

@ -136,10 +136,24 @@ void ti99_cartridge_device::prepare_cartridge()
}
m_pcb->m_rom_size = loaded_through_softlist() ? get_software_region_length("rom") : m_rpk->get_resource_length("rom_socket");
m_pcb->m_bank_mask = 0;
if (m_pcb->m_rom_size > 0)
{
if (m_pcb->m_rom_size > 0x200000) fatalerror("Cartridge ROM size exceeding 2 MiB");
LOGMASKED(LOG_CONFIG, "rom size=0x%04x\n", m_pcb->m_rom_size);
// Determine the bank mask for flexible ROM sizes in gromemu
int rsizet = m_pcb->m_rom_size;
int msizet = 0x2000;
while (msizet < rsizet)
{
m_pcb->m_bank_mask = (m_pcb->m_bank_mask<<1) | 1;
msizet <<= 1;
}
LOGMASKED(LOG_CONFIG, "rom bank mask=0x%04x\n", m_pcb->m_bank_mask);
regr = memregion(CARTROM_TAG);
rom_ptr = loaded_through_softlist() ? get_software_region("rom") : m_rpk->get_contents_of_socket("rom_socket");
memcpy(regr->base(), rom_ptr, m_pcb->m_rom_size);
@ -158,6 +172,11 @@ void ti99_cartridge_device::prepare_cartridge()
regr = memregion(CARTROM_TAG);
rom_ptr = m_rpk->get_contents_of_socket("rom2_socket");
memcpy(regr->base() + 0x2000, rom_ptr, rom2_length);
// Configurations with ROM1+ROM2 have exactly two banks; only
// the first 8K are used from ROM1.
m_pcb->m_bank_mask = 1;
LOGMASKED(LOG_CONFIG, "rom bank mask=0x0001 (using rom/rom2)\n");
}
}
@ -1270,23 +1289,16 @@ void ti99_pagedcru_cartridge::cruwrite(offs_t offset, uint8_t data)
will deliver the address when reading.
- No wait states. Reading is generally faster than with real GROMs.
- No wrapping at 8K boundaries.
- Two pages of ROM at address 6000
If any of these fails, the cartridge will crash, so we'll see.
- One or two ROM sockets; if one socket, the standard bank switch scheme is
used
Typical cartridges: Third-party cartridges
For the sake of simplicity, we register GROMs like the other PCB types, but
we implement special access methods for the GROM space.
Still not working:
rxb1002 (Set page to 1 (6372 <- 00), lockup)
rxb237 (immediate reset)
rxbv555 (repeating reset on Master Title Screen)
superxb (lockup, fix: add RAM at 7c00)
Super-MiniMemory is also included here. We assume a RAM area at addresses
7000-7fff for this cartridge.
7000-7fff for this cartridge if the RAM option is used.
GROM space
@ -1296,10 +1308,22 @@ void ti99_pagedcru_cartridge::cruwrite(offs_t offset, uint8_t data)
ROM space
6000 7000 7fff
| | |
|========== ROM1 ===========| Bank 0 write to 6000, 6004, ... 7ffc
|========== ROM1 ===========| Bank 0
| | |
|========== ROM2 ===========| Bank 1 write to 6002, 6006, ... 7ffe
|========== ROM2 ===========| Bank 1
... ...
|========== ROMn ===========| Bank n-1
Depending on the number of banks, a number of address bits is used to select
the bank:
Write to 011x xxxx xxxx xxx0 -> Set bank number to xxxxxxxxxxxx
The number xxxxxxxxxxxx has just enough bits to encode the highest bank number.
Higher bits are ignored.
If rom2_socket is used, we assume that rom_socket and rom2_socket contain
8K ROM each, so we have exactly two banks, regardless of the ROM length.
******************************************************************************/
@ -1349,7 +1373,9 @@ void ti99_gromemu_cartridge::write(offs_t offset, uint8_t data)
}
return; // no paging
}
m_rom_page = (offset >> 1) & 1;
m_rom_page = (offset >> 1) & m_bank_mask;
if ((offset & 1)==0)
LOGMASKED(LOG_BANKSWITCH, "Set ROM page = %d (writing to %04x)\n", m_rom_page, (offset | 0x6000));
}

1
src/devices/bus/ti99/gromport/cartridges.h
View File

@ -236,6 +236,7 @@ protected:
int m_grom_size;
int m_rom_size;
int m_ram_size;
int m_bank_mask;
uint8_t* m_rom_ptr;
uint8_t* m_ram_ptr;