Differences

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--- system_interface [2025/07/03 16:11] – reggie
+++ system_interface [2025/07/25 17:52] (current) – reggie
@@ Line 5: / Line 5: @@
   const SIbaseAddress=$ff80
   const SIrefreshOff=0, SIrefreshOn=1, SIgraphicsMode=2, SIkeyInterface=3;
+  const SIArrowButtons=4;
   SIrefreshOff       Write <any> to force OFF register refresh and display animation
@@ Line 10: / Line 11: @@
   SIgraphicsMode     Write <number of colours> to select graphics mode (2, 4, 16 allowed values)
   SIkeyInterface     Write 0 then read an ASCII code (if<128), write 255 to clear the keyboard buffer
+  SIArrowButtons     Read state of game controller buttons
 ==== Refresh ====
@@ Line 45: / Line 47: @@
 === Graphics Screen Layout ===
-In all modes the graphics RAM beings at $0600 and is 6K bytes long. In 2 colour mode it is 256 pixels wide by 192 pixels high. It is conventional to map the display with the top-left at (0,0) and the bottom right at (255,191) using the same virtual coordinates whatever the colour mode. Therefore in 4-colour mode pixels are 2*1 units in size, and in 15-colour mode 2*2 units.
+In all modes the graphics RAM beings at $0600 and is 6K bytes long. In 2 colour mode it is 256 pixels wide by 192 pixels high. It is conventional to map the display with the top-left at (0,0) and the bottom right at (255,191) using the same virtual coordinates whatever the colour mode. Therefore in 4-colour mode pixels are 2*1 units in size, and in 16-colour mode 2*2 units.
   const grxBase=$0600, grxSize=$1800, gLineBytes2=$20, gLineBytes4=$20, gLineBytes16=$40
@@ Line 71: / Line 73: @@
     cmpa #escape                       ; flag Zero if ESC
     rts
+A game controller is emulated using the keyboard. The arrow keys are for movement, plus Space and Enter can be used for 'Fire' and 'Bomb'. You can see their activity below the text screen. Read from the port to get a bitmap of these keys; logical AND with the appropriate mask to test whether a button is currently pressed or not. Note that these keys may interfere with normal functions of the HTML page such as scrolling and editing; click the Halt or Reset buttons to stop this.
+  const ArrowLeft=$01, ArrowRight=$02, ArrowUp=$04, ArrowDown=$08
+  const BtnFire=$10, BtnBomb=$20
+  readControls:
+    lda SIBaseAddress+SIArrowButtons
+    bita #BtnFire
+    bne fireWeapon