// license:BSD-3-Clause
// copyright-holders:Curt Coder
/**********************************************************************
CD40105/HC40105 4-bit x 16-word FIFO Register
Part of the 4000B series of CMOS logic devices, the 40105 includes
an asynchronous master reset pin intended to be connected to the
system bus.
Word size can be expanded from 4 bits to 8 bits by connecting two
40105s in parallel, with external AND gates to combine the DIR and
DOR outputs. They can also be connected in series to extend the
FIFO capacity, with DOR -> SI and /SO <- DIR.
**********************************************************************/
#include "emu.h"
#include "40105.h"
//**************************************************************************
// MACROS / CONSTANTS
//**************************************************************************
#define LOG 0
//**************************************************************************
// DEVICE DEFINITIONS
//**************************************************************************
DEFINE_DEVICE_TYPE(CD40105, cmos_40105_device, "cd40105", "CD40105B FIFO Register")
//**************************************************************************
// LIVE DEVICE
//**************************************************************************
//-------------------------------------------------
// cmos_40105_device - constructor
//-------------------------------------------------
cmos_40105_device::cmos_40105_device(const machine_config &mconfig, const char *tag, device_t *owner, u32 clock) :
device_t(mconfig, CD40105, tag, owner, clock),
m_write_dir(*this),
m_write_dor(*this),
m_write_q(*this),
m_d(0),
m_q(0),
m_dir(false),
m_dor(false),
m_si(false),
m_so(false)
{
}
//-------------------------------------------------
// device_start - device-specific startup
//-------------------------------------------------
void cmos_40105_device::device_start()
{
// state saving
save_item(NAME(m_d));
save_item(NAME(m_q));
save_item(NAME(m_dir));
save_item(NAME(m_dor));
save_item(NAME(m_si));
save_item(NAME(m_so));
}
//-------------------------------------------------
// device_reset - device-specific reset
//-------------------------------------------------
void cmos_40105_device::device_reset()
{
// invalidate data in queue
m_fifo = std::queue<u8>();
// reset control flip-flops
m_dir = true;
m_dor = false;
m_write_dir(1);
m_write_dor(0);
}
//-------------------------------------------------
// read - read output buffer (Q0 to Q3)
//-------------------------------------------------
u8 cmos_40105_device::read()
{
return m_q;
}
//-------------------------------------------------
// write - write input buffer (D0 to D3)
//-------------------------------------------------
void cmos_40105_device::write(u8 data)
{
m_d = data & 0x0f;
}
//-------------------------------------------------
// load_input - load new data into FIFO
//-------------------------------------------------
void cmos_40105_device::load_input()
{
if (m_fifo.size() == 16)
{
logerror("Attempt to load data into full FIFO\n");
return;
}
m_fifo.push(m_d);
// DIR remains low if FIFO is full, or else briefly pulses low
m_write_dir(0);
if (m_fifo.size() == 16)
m_dir = false;
else
m_write_dir(1);
}
//-------------------------------------------------
// output_ready - place new data at output
//-------------------------------------------------
void cmos_40105_device::output_ready()
{
if (m_fifo.size() == 0)
{
logerror("Attempt to output data from empty FIFO\n");
return;
}
m_q = m_fifo.front();
m_write_q(m_q);
m_dor = true;
m_write_dor(1);
}
//-------------------------------------------------
// si_w - shift in write
//-------------------------------------------------
void cmos_40105_device::si_w(int state)
{
// load input on rising edge when ready
if (m_dir && !m_si && state)
{
load_input();
}
else if (m_si && !state && m_fifo.size() > 0)
{
// data propagates through FIFO when SI goes low
if (!m_dor)
output_ready();
}
m_si = state;
}
//-------------------------------------------------
// so_w - shift out write
//-------------------------------------------------
void cmos_40105_device::so_w(int state)
{
// shift out on falling edge when ready
if (m_dor && m_so && !state)
{
m_fifo.pop();
m_dor = false;
m_write_dor(0);
// DOR remains low if FIFO is now empty, or else briefly pulses low
if (m_fifo.size() > 0)
output_ready();
if (!m_dir)
{
// raise DIR since FIFO is no longer full
m_dir = true;
m_write_dir(1);
// load new input immediately if SI is held high
if (m_si)
load_input();
}
}
m_so = state;
}
//-------------------------------------------------
// dir_r - data in ready read
//-------------------------------------------------
int cmos_40105_device::dir_r()
{
return m_dir;
}
//-------------------------------------------------
// dor_r - data out ready read
//-------------------------------------------------
int cmos_40105_device::dor_r()
{
return m_dor;
}