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/***************************************************************************
i8243.c
Intel 8243 Port Expander
Copyright Aaron Giles
***************************************************************************/
#include "emu.h"
#include "i8243.h"
//**************************************************************************
// LIVE DEVICE
//**************************************************************************
// device type definition
const device_type I8243 = &device_creator<i8243_device>;
//-------------------------------------------------
// i8243_device - constructor
//-------------------------------------------------
i8243_device::i8243_device(const machine_config &mconfig, const char *tag, device_t *owner, UINT32 clock)
: device_t(mconfig, I8243, "I8243", tag, owner, clock, "i8243", __FILE__),
m_readhandler(*this),
m_writehandler(*this)
{
}
//-------------------------------------------------
// device_start - device-specific startup
//-------------------------------------------------
void i8243_device::device_start()
{
m_readhandler.resolve_safe(0);
m_writehandler.resolve_safe();
}
//-------------------------------------------------
// device_reset - device-specific reset
//-------------------------------------------------
void i8243_device::device_reset()
{
m_p2 = 0x0f;
m_p2out = 0x0f;
m_prog = 1;
}
/*-------------------------------------------------
i8243_p2_r - handle a read from port 2
-------------------------------------------------*/
READ8_MEMBER(i8243_device::i8243_p2_r)
{
return m_p2out;
}
/*-------------------------------------------------
i8243_p2_r - handle a write to port 2
-------------------------------------------------*/
WRITE8_MEMBER(i8243_device::i8243_p2_w)
{
m_p2 = data & 0x0f;
}
/*-------------------------------------------------
i8243_prog_w - handle a change in the PROG
line state
-------------------------------------------------*/
WRITE8_MEMBER(i8243_device::i8243_prog_w)
{
/* only care about low bit */
data &= 1;
/* on high->low transition state, latch opcode/port */
if(m_prog && !data)
{
m_opcode = m_p2;
/* if this is a read opcode, copy result to p2out */
if((m_opcode >> 2) == MCS48_EXPANDER_OP_READ)
{
if (m_readhandler.isnull())
{
m_p[m_opcode & 3] = m_readhandler(m_opcode & 3);
}
m_p2out = m_p[m_opcode & 3] & 0x0f;
}
}
/* on low->high transition state, act on opcode */
else if(!m_prog && data)
{
switch(m_opcode >> 2)
{
case MCS48_EXPANDER_OP_WRITE:
m_p[m_opcode & 3] = m_p2 & 0x0f;
m_writehandler((offs_t)(m_opcode & 3), m_p[m_opcode & 3]);
break;
case MCS48_EXPANDER_OP_OR:
m_p[m_opcode & 3] |= m_p2 & 0x0f;
m_writehandler((offs_t)(m_opcode & 3), m_p[m_opcode & 3]);
break;
case MCS48_EXPANDER_OP_AND:
m_p[m_opcode & 3] &= m_p2 & 0x0f;
m_writehandler((offs_t)(m_opcode & 3), m_p[m_opcode & 3]);
break;
}
}
/* remember the state */
m_prog = data;
}
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