Improve status register update responsiveness

Author: tschrapel

CMakeLists.txt

@@ -16,10 +16,7 @@ set(PICO_BOARD "pico9918_v04")
 project(${PROJECT} C CXX)
 
 add_definitions(-DPICO_BUILD=1)
-add_definitions(-DPICO_DISABLE_SHARED_IRQ_HANDLERS=1)
 add_definitions(-DVR_EMU_TMS9918_SINGLE_INSTANCE=1)
-add_definitions(-DPICO_PANIC_FUNCTION=)
-add_definitions(-DPICO_TIME_DEFAULT_ALARM_POOL_DISABLED=1)
 
 set(CMAKE_C_STANDARD 11)
 set(CMAKE_CXX_STANDARD 17)

src/CMakeLists.txt

@@ -19,6 +19,10 @@ pico_enable_stdio_uart(${PROGRAM} 0)
 
 pico_set_binary_type(${PROGRAM} copy_to_ram)   # TOO SLOW TO BOOT
 
+add_definitions(-DPICO_DISABLE_SHARED_IRQ_HANDLERS=1)
+add_definitions(-DPICO_TIME_DEFAULT_ALARM_POOL_DISABLED=1)
+add_definitions(-DPICO_PANIC_FUNCTION=)
+
 target_link_libraries(${PROGRAM} PUBLIC
         pico_stdlib
         pico_multicore

src/main.c

@@ -111,7 +111,7 @@
 
 static uint8_t nextValue = 0;     /* TMS9918A read-ahead value */
 static bool currentInt = false;   /* current interrupt state */
-static uint8_t currentStatus = 0; /* current status register value */
+static uint8_t currentStatus = 0x1f; /* current status register value */
 
 static uint8_t __aligned(4) tmsScanlineBuffer[TMS9918_PIXELS_X];
 
@@ -164,7 +164,7 @@ void  __not_in_flash_func(pio_irq_handler)()
     }
     else // read status
     {
-      currentStatus = 0;
+      currentStatus = 0x1f;
       vrEmuTms9918SetStatusImpl(currentStatus);
       currentInt = false;
       gpio_put(GPIO_INT, !currentInt);
@@ -269,12 +269,6 @@ static void __time_critical_func(tmsScanline)(uint16_t y, VgaParams* params, uin
 
   y -= vBorder;
 
-  /*** left border ***/
-  for (int x = 0; x < hBorder; ++x)
-  {
-    pixels[x] = bg;
-  }
-
   /*** main display region ***/
 
   /* generate the scanline */
@@ -286,6 +280,25 @@ static void __time_critical_func(tmsScanline)(uint16_t y, VgaParams* params, uin
     tempStatus |= STATUS_INT;
   }
 
+  disableTmsPioInterrupts();
+  if ((currentStatus & STATUS_INT) == 0)
+  {
+    currentStatus = (currentStatus & 0xe0) | tempStatus;
+
+    vrEmuTms9918SetStatusImpl(currentStatus);
+    updateTmsReadAhead();
+
+    currentInt = vrEmuTms9918InterruptStatusImpl();
+    gpio_put(GPIO_INT, !currentInt);
+  }
+  enableTmsPioInterrupts();
+
+  /*** left border ***/
+  for (int x = 0; x < hBorder; ++x)
+  {
+    pixels[x] = bg;
+  }
+
   /* convert from  palette to bgr12 */
   int tmsX = 0;
   if (tmsScanlineBuffer[0] & 0xf0)
@@ -305,31 +318,13 @@ static void __time_critical_func(tmsScanline)(uint16_t y, VgaParams* params, uin
     }
   }
 
+
   /*** right border ***/
   for (int x = hBorder + TMS9918_PIXELS_X * 2; x < VIRTUAL_PIXELS_X; ++x)
   {
     pixels[x] = bg;
   }
 
-  disableTmsPioInterrupts();
-  if ((currentStatus & STATUS_INT) == 0)
-  {
-    if ((currentStatus & STATUS_5S) != 0)
-    {
-      currentStatus |= tempStatus & 0xe0;
-    }
-    else
-    {
-      currentStatus |= tempStatus;
-    }
-
-    vrEmuTms9918SetStatusImpl(currentStatus);
-    updateTmsReadAhead();
-
-    currentInt = vrEmuTms9918InterruptStatusImpl();
-    gpio_put(GPIO_INT, !currentInt);
-  }
-  enableTmsPioInterrupts();
 }
 
 /*

submodules/vrEmuTms9918

@@ -1,5 +1,5 @@
 cmake_minimum_required(VERSION 3.12)
 
 add_subdirectory(host)
-#add_subdirectory(qc)
+add_subdirectory(qc)