hp64k: DMA added to HP hybrid CPU (working?)

src/emu/cpu/hphybrid/hphybrid.c

@@ -42,6 +42,7 @@ enum {
 #define HPHYBRID_IRL_BIT	9	// IRL requested
 #define HPHYBRID_IRH_SVC_BIT	10	// IRH in service
 #define HPHYBRID_IRL_SVC_BIT	11	// IRL in service
+#define HPHYBRID_DMAR_BIT       12      // DMA request
 
 #define HPHYBRID_IV_MASK        0xfff0  // IV mask
 
@@ -51,6 +52,15 @@ enum {
 
 const device_type HP_5061_3011 = &device_creator<hp_5061_3011_cpu_device>;
 
+WRITE_LINE_MEMBER(hp_hybrid_cpu_device::dmar_w)
+{
+        if (state) {
+                BIT_SET(m_flags , HPHYBRID_DMAR_BIT);
+        } else {
+                BIT_CLR(m_flags , HPHYBRID_DMAR_BIT);
+        }
+}
+
 hp_hybrid_cpu_device::hp_hybrid_cpu_device(const machine_config &mconfig, device_type type, const char *name, const char *tag, device_t *owner, UINT32 clock, const char *shortname)
 : cpu_device(mconfig, type, name, tag, owner, clock, shortname, __FILE__),
         m_program_config("program", ENDIANNESS_BIG, 16, 16, -1),
@@ -127,13 +137,16 @@ void hp_hybrid_cpu_device::device_reset()
 void hp_hybrid_cpu_device::execute_run()
 {
         do {
+                if (BIT(m_flags , HPHYBRID_DMAEN_BIT) && BIT(m_flags , HPHYBRID_DMAR_BIT)) {
+                        handle_dma();
+                } else {
                         debugger_instruction_hook(this, m_reg_P);
 
                         // Check for interrupts
                         check_for_interrupts();
 
-                // TODO: check dma
                         m_reg_I = execute_one(m_reg_I);
+                }
         } while (m_icount > 0);
 }
 
@@ -768,6 +781,32 @@ void hp_hybrid_cpu_device::check_for_interrupts(void)
         m_reg_I = RM(m_reg_P);
 }
 
+void hp_hybrid_cpu_device::handle_dma(void)
+{
+        // Patent hints at the fact that terminal count is detected by bit 15 of dmac being 1 after decrementing
+        bool tc = BIT(--m_dmac , 15) != 0;
+        UINT16 tmp;
+
+        if (BIT(m_flags , HPHYBRID_DMADIR_BIT)) {
+                // "Outward" DMA: memory -> peripheral
+                tmp = RM(m_dmama++);
+                WIO(m_dmapa , tc ? 2 : 0 , tmp);
+                m_icount -= 10;
+        } else {
+                // "Inward" DMA: peripheral -> memory
+                tmp = RIO(m_dmapa , tc ? 2 : 0);
+                WM(m_dmama++ , tmp);
+                m_icount -= 9;
+        }
+
+        // This is the one of the biggest question marks: is the DMA automatically disabled on TC?
+        // Here we assume it is. After all it would make no difference because there is no way
+        // to read the DMA enable flag back, so each time the DMA is needed it has to be enabled again.
+        if (tc) {
+                BIT_CLR(m_flags , HPHYBRID_DMAEN_BIT);
+        }
+}
+
 UINT16 hp_hybrid_cpu_device::RM(UINT16 addr)
 {
         UINT16 tmp;

src/emu/cpu/hphybrid/hphybrid.h

@@ -65,6 +65,8 @@
 class hp_hybrid_cpu_device : public cpu_device
 {
 public:
+        DECLARE_WRITE_LINE_MEMBER(dmar_w);
+
 protected:
         hp_hybrid_cpu_device(const machine_config &mconfig, device_type type, const char *name, const char *tag, device_t *owner, UINT32 clock, const char *shortname);
     
@@ -124,6 +126,7 @@ private:
         UINT16 get_skip_addr_sc(UINT16 opcode , UINT16& v , unsigned n);
         void do_pw(UINT16 opcode);
         void check_for_interrupts(void);
+        void handle_dma(void);
     
         UINT16 RM(UINT16 addr);
         void   WM(UINT16 addr , UINT16 v);