// license:BSD-3-Clause // copyright-holders:Juergen Buchmueller /***************************************************************************** * * Xerox AltoII display horizontal task * *****************************************************************************/ #include "emu.h" #include "alto2cpu.h" /* * Copied from ALTOCODE24.MU * ;Display Horizontal Task. * ;11 cycles if no block change, 17 if new control block. * * DHT: MAR← CBA-1; * L← SLC -1, BUS=0; * SLC← L, :DHT0; * * DHT0: T← 37400; MORE TO DO IN THIS BLOCK * SINK← MD; * L← T← MD AND T, SETMODE; * HTAB← L LCY 8, :NORMODE; * * NORMODE:L← T← 377 . T; * AECL← L, :REST; * * HALFMODE: L← T← 377 . T; * AECL← L, :REST, T← 0; * * REST: L← DWA + T,TASK; INCREMENT DWA BY 0 OR NWRDS * NDNX: DWA← L, :DHT; * * DHT1: L← T← MD+1, BUS=0; * CBA← L, MAR← T, :MOREB; * * NOMORE: BLOCK, :DNX; * MOREB: T← 37400; * L← T← MD AND T, SETMODE; * MAR← CBA+1, :NORMX, EVENFIELD; * * NORMX: HTAB← L LCY 8, :NODD; * HALFX: HTAB← L LCY 8, :NEVEN; * * NODD: L←T← 377 . T; * AECL← L, :XREST; ODD FIELD, FULL RESOLUTION * * NEVEN: L← 377 AND T; EVEN FIELD OR HALF RESOLUTION * AECL←L, T←0; * * XREST: L← MD+T; * T←MD-1; * DNX: DWA←L, L←T, TASK; * SLC←L, :DHT; */ /** * @brief f1_dht_block early: disable the display word task */ void alto2_cpu_device::f1_early_dht_block() { m_dsp.dht_blocks = true; // clear the wakeup for the display horizontal task m_task_wakeup &= ~(1 << m_task); LOG((this,LOG_DHT,2," BLOCK %s\n", task_name(m_task))); } /** * @brief f2_dht_setmode late: set the next scanline's mode inverse and half clock and branch * * BUS[0] selects the pixel clock (0), or half pixel clock (1) * BUS[1] selects normal mode (0), or inverse mode (1) * * The current BUS[0] drives the NEXT[09] line, i.e. branches to 0 or 1 */ void alto2_cpu_device::f2_late_dht_setmode() { uint16_t r = X_RDBITS(m_bus,16,0,0); m_dsp.setmode = m_bus; LOG((this,LOG_DHT,2," SETMODE<- BUS (%#o), branch on BUS[0] (%#o | %#o)\n", m_bus, m_next2, r)); m_next2 |= r; } /** * @brief called by the CPU when the display horizontal task becomes active */ void alto2_cpu_device::activate_dht() { m_task_wakeup &= ~(1 << m_task); } /** * @brief initialize the display horizontal task * * @param task task number */ void alto2_cpu_device::init_dht(int task) { } void alto2_cpu_device::exit_dht() { // nothing to do yet } void alto2_cpu_device::reset_dht() { m_dsp.dht_blocks = true; m_dsp.setmode = 0; }