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some notes from charles

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This commit is contained in:
Michaël Banaan Ananas 2014-10-10 15:56:23 +00:00
parent f0fad04eb6
commit a6ca34b6ee
2 changed files with 27 additions and 7 deletions
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3
src/mame/drivers/segac2.c
View File

@ -417,7 +417,6 @@ READ8_MEMBER(segac2_state::io_portc_r)
// D6 : From uPD7759 pin 18. (/BUSY output)
int busy = (m_upd7759 != NULL) ? (m_upd7759->busy_r() << 6) : 0x40;
return 0xbf | busy;
}
WRITE8_MEMBER(segac2_state::io_portd_w)
@ -1375,7 +1374,7 @@ static MACHINE_CONFIG_START( segac, segac2_state )
MCFG_MACHINE_RESET_OVERRIDE(segac2_state,segac2)
MCFG_NVRAM_ADD_1FILL("nvram") // borencha requires 0xff fill or there is no sound (it lacks some of the init code of the borench set)
MCFG_DEVICE_ADD("io", SEGA_315_5296, 0)
MCFG_DEVICE_ADD("io", SEGA_315_5296, XL2_CLOCK/6) // clock divider guessed
MCFG_315_5296_IN_PORTA_CB(IOPORT("P1"))
MCFG_315_5296_IN_PORTB_CB(IOPORT("P2"))
MCFG_315_5296_IN_PORTC_CB(READ8(segac2_state, io_portc_r))

31
src/mame/machine/315-5296.c
View File

@ -3,8 +3,21 @@
Sega 315-5296 I/O chip
Sega 100-pin QFP, with 8 bidirectional I/O ports, and 3 output pins.
It also has chip select(/FMCS) and clock(CKOT) for a peripheral device.
Commonly used from the late 80s up until Sega Model 2.
The I/O chip has 64 addresses:
$00-0F : I/O ports, security, configuration registers
$10-1F : Unused (no effect when read or written)
$20-3F : Unused (enables /FMCS output, eg. to YM2151 /CS)
On System 16 derivatives, the unused locations return the 68000 prefetch
value off the bus when read.
TODO:
- complete emulation of CNT register
**********************************************************************/
#include "machine/315-5296.h"
@ -16,7 +29,6 @@ const device_type SEGA_315_5296 = &device_creator<sega_315_5296_device>;
// sega_315_5296_device - constructor
//-------------------------------------------------
sega_315_5296_device::sega_315_5296_device(const machine_config &mconfig, const char *tag, device_t *owner, UINT32 clock)
: device_t(mconfig, SEGA_315_5296, "Sega 315-5296", tag, owner, clock, "315-5296", __FILE__),
m_in_pa_cb(*this),
@ -100,7 +112,7 @@ void sega_315_5296_device::device_reset()
READ8_MEMBER( sega_315_5296_device::read )
{
offset &= 0xf;
offset &= 0x3f;
switch (offset)
{
@ -109,7 +121,7 @@ READ8_MEMBER( sega_315_5296_device::read )
// if the port is configured as an output, return the last thing written
if (m_dir & 1 << offset)
return m_output_latch[offset];
// otherwise, return an input port
return (*m_in_port_cb[offset])(offset);
@ -130,6 +142,9 @@ READ8_MEMBER( sega_315_5296_device::read )
// port direction register & mirror
case 0xd: case 0xf:
return m_dir;
default:
break;
}
return 0xff;
@ -138,7 +153,7 @@ READ8_MEMBER( sega_315_5296_device::read )
WRITE8_MEMBER( sega_315_5296_device::write )
{
offset &= 0xf;
offset &= 0x3f;
switch (offset)
{
@ -153,10 +168,16 @@ WRITE8_MEMBER( sega_315_5296_device::write )
// CNT register
case 0xe:
// d0-2: CNT0-2, other bits: ?
// d0-2: CNT0-2 output pins
// note: When CNT2 is configured as clock output, bit 2 of this register has
// no effect on the output level of CNT2.
for (int i = 0; i < 3; i++)
(*m_out_cnt_cb[i])(data >> i & 1);
// d3: CNT2 output mode (1= Clock output, 0= Programmable output)
// d4,5: CNT2 clock divider (0= CLK/4, 1= CLK/8, 2= CLK/16, 3= CLK/2)
// d6,7: CKOT clock divider (0= CLK/4, 1= CLK/8, 2= CLK/16, 3= CLK/2)
// TODO..
m_cnt = data;
break;