mirror of
https://github.com/holub/mame
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114 lines
2.8 KiB
C++
114 lines
2.8 KiB
C++
// license:BSD-3-Clause
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// copyright-holders:Juergen Buchmueller
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/*****************************************************************************
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*
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* Xerox AltoII display horizontal task
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*
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*****************************************************************************/
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#include "alto2cpu.h"
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/*
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* Copied from ALTOCODE24.MU
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* ;Display Horizontal Task.
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* ;11 cycles if no block change, 17 if new control block.
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*
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* DHT: MAR← CBA-1;
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* L← SLC -1, BUS=0;
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* SLC← L, :DHT0;
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*
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* DHT0: T← 37400; MORE TO DO IN THIS BLOCK
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* SINK← MD;
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* L← T← MD AND T, SETMODE;
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* HTAB← L LCY 8, :NORMODE;
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*
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* NORMODE:L← T← 377 . T;
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* AECL← L, :REST;
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*
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* HALFMODE: L← T← 377 . T;
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* AECL← L, :REST, T← 0;
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*
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* REST: L← DWA + T,TASK; INCREMENT DWA BY 0 OR NWRDS
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* NDNX: DWA← L, :DHT;
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*
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* DHT1: L← T← MD+1, BUS=0;
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* CBA← L, MAR← T, :MOREB;
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*
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* NOMORE: BLOCK, :DNX;
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* MOREB: T← 37400;
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* L← T← MD AND T, SETMODE;
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* MAR← CBA+1, :NORMX, EVENFIELD;
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*
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* NORMX: HTAB← L LCY 8, :NODD;
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* HALFX: HTAB← L LCY 8, :NEVEN;
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*
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* NODD: L←T← 377 . T;
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* AECL← L, :XREST; ODD FIELD, FULL RESOLUTION
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*
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* NEVEN: L← 377 AND T; EVEN FIELD OR HALF RESOLUTION
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* AECL←L, T←0;
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*
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* XREST: L← MD+T;
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* T←MD-1;
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* DNX: DWA←L, L←T, TASK;
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* SLC←L, :DHT;
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*/
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/**
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* @brief f1_dht_block early: disable the display word task
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*/
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void alto2_cpu_device::f1_early_dht_block()
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{
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m_dsp.dht_blocks = true;
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// clear the wakeup for the display horizontal task
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m_task_wakeup &= ~(1 << m_task);
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LOG((this,LOG_DHT,2," BLOCK %s\n", task_name(m_task)));
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}
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/**
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* @brief f2_dht_setmode late: set the next scanline's mode inverse and half clock and branch
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*
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* BUS[0] selects the pixel clock (0), or half pixel clock (1)
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* BUS[1] selects normal mode (0), or inverse mode (1)
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*
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* The current BUS[0] drives the NEXT[09] line, i.e. branches to 0 or 1
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*/
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void alto2_cpu_device::f2_late_dht_setmode()
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{
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UINT16 r = X_RDBITS(m_bus,16,0,0);
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m_dsp.setmode = m_bus;
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LOG((this,LOG_DHT,2," SETMODE<- BUS (%#o), branch on BUS[0] (%#o | %#o)\n", m_bus, m_next2, r));
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m_next2 |= r;
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}
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/**
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* @brief called by the CPU when the display horizontal task becomes active
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*/
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void alto2_cpu_device::activate_dht()
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{
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m_task_wakeup &= ~(1 << m_task);
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}
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/**
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* @brief initialize the display horizontal task
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*
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* @param task task number
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*/
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void alto2_cpu_device::init_dht(int task)
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{
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set_f1(task, f1_block, &alto2_cpu_device::f1_early_dht_block, nullptr);
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set_f2(task, f2_dht_evenfield, nullptr, &alto2_cpu_device::f2_late_evenfield);
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set_f2(task, f2_dht_setmode, nullptr, &alto2_cpu_device::f2_late_dht_setmode);
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m_active_callback[task] = &alto2_cpu_device::activate_dht;
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}
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void alto2_cpu_device::exit_dht()
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{
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// nothing to do yet
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}
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void alto2_cpu_device::reset_dht()
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{
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m_dsp.dht_blocks = true;
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m_dsp.setmode = 0;
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}
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