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/*
spchroms.c - This is an emulator for "typical" speech ROMs from TI, as used by TI99/4(a).
In order to support its speech processor, TI designed some ROMs with a 1-bit data bus
and 4-bit address bus (multiplexed 5 times to provide a 18-bit address).
A fairly complete description of such a ROM (tms6100) is found in the tms5220 datasheet.
One notable thing is that the address is a byte address (*NOT* a bit address).
This file is designed to be interfaced with the tms5220 core.
Interfacing it with the tms5110 would make sense, too.
TODO:
Create seperate devices for TMS6100 & TMS6125
Implement the serial protocol
*/
#include "emu.h"
#include "spchrom.h"
#define TMS5220_ADDRESS_MASK 0x3FFFFUL /* 18-bit mask for tms5220 address */
// device type definition
const device_type SPEECHROM = &device_creator<speechrom_device>;
speechrom_device::speechrom_device(const machine_config &mconfig, const char *tag, device_t *owner, UINT32 clock)
: device_t(mconfig, SPEECHROM, "SPEECHROM", tag, owner, clock),
m_speechROMaddr(0),
m_load_pointer(0),
m_ROM_bits_count(0)
{
}
/*
Read 'count' bits serially from speech ROM
*/
int speechrom_device::read(int count)
{
int val;
if (m_load_pointer)
{ /* first read after load address is ignored */
m_load_pointer = 0;
count--;
}
if (m_speechROMaddr < m_speechROMlen)
if (count < m_ROM_bits_count)
{
m_ROM_bits_count -= count;
val = (m_speechrom_data[m_speechROMaddr] >> m_ROM_bits_count) & (0xFF >> (8 - count));
}
else
{
val = ((int) m_speechrom_data[m_speechROMaddr]) << 8;
m_speechROMaddr = (m_speechROMaddr + 1) & TMS5220_ADDRESS_MASK;
if (m_speechROMaddr < m_speechROMlen)
val |= m_speechrom_data[m_speechROMaddr];
m_ROM_bits_count += 8 - count;
val = (val >> m_ROM_bits_count) & (0xFF >> (8 - count));
}
else
val = 0;
return val;
}
/*
Write an address nibble to speech ROM
*/
void speechrom_device::load_address(int data)
{
/* tms5220 data sheet says that if we load only one 4-bit nibble, it won't work.
This code does not care about this. */
m_speechROMaddr = ( (m_speechROMaddr & ~(0xf << m_load_pointer))
| (((unsigned long) (data & 0xf)) << m_load_pointer) ) & TMS5220_ADDRESS_MASK;
m_load_pointer += 4;
m_ROM_bits_count = 8;
}
/*
Perform a read and branch command
*/
void speechrom_device::read_and_branch()
{
/* tms5220 data sheet says that if more than one speech ROM (tms6100) is present,
there is a bus contention. This code does not care about this. */
if (m_speechROMaddr < m_speechROMlen-1)
m_speechROMaddr = (m_speechROMaddr & 0x3c000UL)
| (((((unsigned long) m_speechrom_data[m_speechROMaddr]) << 8)
| m_speechrom_data[m_speechROMaddr+1]) & 0x3fffUL);
else if (m_speechROMaddr == m_speechROMlen-1)
m_speechROMaddr = (m_speechROMaddr & 0x3c000UL)
| ((((unsigned long) m_speechrom_data[m_speechROMaddr]) << 8) & 0x3fffUL);
else
m_speechROMaddr = (m_speechROMaddr & 0x3c000UL);
m_ROM_bits_count = 8;
}
void speechrom_device::device_start()
{
memory_region *region = memregion(tag());
if (region == NULL)
{
throw emu_fatalerror("No region for device '%s'\n", tag());
}
m_speechrom_data = region->base();
m_speechROMlen = region->bytes();
save_item(NAME(m_speechROMaddr));
save_item(NAME(m_load_pointer));
save_item(NAME(m_ROM_bits_count));
}
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