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Diffstat (limited to 'src/devices/cpu/alto2/a2dht.cpp')
-rw-r--r--src/devices/cpu/alto2/a2dht.cpp67
1 files changed, 67 insertions, 0 deletions
diff --git a/src/devices/cpu/alto2/a2dht.cpp b/src/devices/cpu/alto2/a2dht.cpp
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+++ b/src/devices/cpu/alto2/a2dht.cpp
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+// license:BSD-3-Clause
+// copyright-holders:Juergen Buchmueller
+/*****************************************************************************
+ *
+ * Xerox AltoII display horizontal task
+ *
+ *****************************************************************************/
+#include "alto2cpu.h"
+
+/**
+ * @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 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)
+{
+ set_f1(task, f1_block, &alto2_cpu_device::f1_early_dht_block, 0);
+ set_f2(task, f2_dht_evenfield, 0, &alto2_cpu_device::f2_late_evenfield);
+ set_f2(task, f2_dht_setmode, 0, &alto2_cpu_device::f2_late_dht_setmode);
+ m_active_callback[task] = &alto2_cpu_device::activate_dht;
+}
+
+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;
+}