From 3df5232ca46a76bca012e575297cbfb93753125d Mon Sep 17 00:00:00 2001
From: "Kartik K. Agaram" <vc@akkartik.com>
Date: Tue, 29 Jun 2021 22:12:32 -0700
Subject: timer and keyboard handlers working together

---
 timer.subx | 62 ++++++++++++++++++++++++++++++++++++++++++++------------------
 1 file changed, 44 insertions(+), 18 deletions(-)

diff --git a/timer.subx b/timer.subx
index 5a317c91..89c5ef6d 100644
--- a/timer.subx
+++ b/timer.subx
@@ -293,11 +293,11 @@ idt_start:
   0/imm16  # target[16:32] -- timer-interrupt-handler must be within address 0x10000
 
 # entry 9: keyboard
-  null-interrupt-handler/imm16  # target[0:16]
+  keyboard-interrupt-handler/imm16  # target[0:16]
   8/imm16  # segment selector (gdt_code)
   00  # unused
   8e  # 1/p 00/dpl 0 1110/type/32-bit-interrupt-gate
-  0/imm16  # target[16:32] -- null-interrupt-handler must be within address 0x10000
+  0/imm16  # target[16:32] -- keyboard-interrupt-handler must be within address 0x10000
 
 00 00 00 00 00 00 00 00
 00 00 00 00 00 00 00 00
@@ -326,22 +326,6 @@ idt_start:
 
 == code
 
-null-interrupt-handler:
-  # prologue
-  fa/disable-interrupts
-  60/push-all-registers
-  9c/push-flags
-  # acknowledge interrupt
-  b0/copy-to-al 0x20/imm8
-  e6/write-al-into-port 0x20/imm8
-  31/xor %eax 0/r32/eax
-$null-interrupt-handler:epilogue:
-  # epilogue
-  9d/pop-flags
-  61/pop-all-registers
-  fb/enable-interrupts
-  cf/return-from-interrupt
-
 timer-interrupt-handler:
   # prologue
   fa/disable-interrupts
@@ -375,6 +359,45 @@ $timer-interrupt-handler:epilogue:
   fb/enable-interrupts
   cf/return-from-interrupt
 
+keyboard-interrupt-handler:
+  # prologue
+  fa/disable-interrupts
+  60/push-all-registers
+  9c/push-flags
+  # acknowledge interrupt
+  b0/copy-to-al 0x20/imm8
+  e6/write-al-into-port 0x20/imm8
+  31/xor %eax 0/r32/eax
+  # check output buffer of 8042 keyboard controller (https://web.archive.org/web/20040604041507/http://panda.cs.ndsu.nodak.edu/~achapwes/PICmicro/keyboard/atkeyboard.html)
+  e4/read-port-into-al 0x64/imm8
+  a8/test-bits-in-al 0x01/imm8  # set zf if bit 0 (least significant) is not set
+  0f 84/jump-if-not-set $keyboard-interrupt-handler:epilogue/disp32
+  # initialize current-pixel-location if necessary
+  81 7/subop/compare *Keyboard-current-pixel 0/imm32
+  {
+    75/jump-if-!= break/disp8
+    8b/-> *Video-memory-addr 1/r32/ecx
+    89/<- *Keyboard-current-pixel 1/r32/ecx
+  }
+  # - read keycode
+  e4/read-port-into-al 0x60/imm8
+  # if (al & 0x80) a key is being lifted; return
+  50/push-eax
+  24/and-al-with 0x80/imm8
+  3c/compare-al-and 0/imm8
+  58/pop-to-eax
+  75/jump-if-!= $keyboard-interrupt-handler:epilogue/disp8
+  # key pressed
+  8b/-> *Keyboard-current-pixel 1/r32/ecx
+  c6 0/subop/copy-byte *ecx 0x31/imm8/green
+  ff 0/subop/increment *Keyboard-current-pixel
+$keyboard-interrupt-handler:epilogue:
+  # epilogue
+  9d/pop-flags
+  61/pop-all-registers
+  fb/enable-interrupts
+  cf/return-from-interrupt
+
 == data
 
 Video-mode-info:
@@ -435,4 +458,7 @@ Video-memory-addr:
 Timer-current-color:
   0/imm32
 
+Keyboard-current-pixel:
+  0/imm32
+
 # vim:ft=subx
-- 
cgit 1.4.1-2-gfad0