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Diffstat (limited to 'src/devices/cpu/alto2/a2dwt.cpp')
-rw-r--r--src/devices/cpu/alto2/a2dwt.cpp62
1 files changed, 62 insertions, 0 deletions
diff --git a/src/devices/cpu/alto2/a2dwt.cpp b/src/devices/cpu/alto2/a2dwt.cpp
new file mode 100644
index 00000000000..b5fd716617c
--- /dev/null
+++ b/src/devices/cpu/alto2/a2dwt.cpp
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+// license:BSD-3-Clause
+// copyright-holders:Juergen Buchmueller
+/*****************************************************************************
+ *
+ * Xerox AltoII display word task
+ *
+ *****************************************************************************/
+#include "alto2cpu.h"
+
+//! PROM a38 bit O1 is STOPWAKE' (stop DWT if bit is zero)
+#define FIFO_STOPWAKE(a38) (0 == (a38 & disp_a38_STOPWAKE) ? true : false)
+
+/**
+ * @brief block the display word task
+ */
+void alto2_cpu_device::f1_early_dwt_block()
+{
+ m_dsp.dwt_blocks = true;
+
+ /* clear the wakeup for the display word task */
+ m_task_wakeup &= ~(1 << m_task);
+ LOG((this,LOG_DWT,2," BLOCK %s\n", task_name(m_task)));
+
+ /* wakeup the display horizontal task, if it didn't block itself */
+ if (!m_dsp.dht_blocks)
+ m_task_wakeup |= 1 << task_dht;
+}
+
+/**
+ * @brief load the display data register
+ */
+void alto2_cpu_device::f2_late_dwt_load_ddr()
+{
+ LOG((this,LOG_DWT,2," DDR<- BUS (%#o)\n", m_bus));
+ m_dsp.fifo[m_dsp.wa] = m_bus;
+ m_dsp.wa = (m_dsp.wa + 1) % ALTO2_DISPLAY_FIFO;
+ UINT8 a38 = m_disp_a38[m_dsp.ra * 16 + m_dsp.wa];
+ if (FIFO_STOPWAKE(a38))
+ m_task_wakeup &= ~(1 << task_dwt);
+ LOG((this,LOG_DWT,2, " DWT push %04x into FIFO[%02o]%s\n",
+ m_bus, (m_dsp.wa - 1) & (ALTO2_DISPLAY_FIFO - 1),
+ FIFO_STOPWAKE(a38) ? " STOPWAKE" : ""));
+}
+
+void alto2_cpu_device::init_dwt(int task)
+{
+ set_f1(task, f1_block, &alto2_cpu_device::f1_early_dwt_block, 0);
+ set_f2(task, f2_dwt_load_ddr, 0, &alto2_cpu_device::f2_late_dwt_load_ddr);
+}
+
+void alto2_cpu_device::exit_dwt()
+{
+ // nothing to do yet
+}
+
+void alto2_cpu_device::reset_dwt()
+{
+ m_dsp.dwt_blocks = false;
+ memset(m_dsp.fifo, 0, sizeof(m_dsp.fifo));
+ m_dsp.wa = 0;
+ m_dsp.ra = 0;
+}