Start working on reading custom charset

3 files changed, 47 insertions, 22 deletions

diff --git a/asm/bootstrap.atk16 b/asm/bootstrap.atk16
index 2aa5d88..31b61f2 100644
--- a/asm/bootstrap.atk16
+++ b/asm/bootstrap.atk16
@@ -1,6 +1,6 @@
 ; vector table fields
 @let vector_table    0x10
-@let vt_ISRO         0x10 ; ISR0
+@let vt_ISR0         0x10 ; ISR0
 @let vt_ISR1         0x11 ; ISR1
 @let vt_ISR2         0x12 ; ISR2
 @let vt_ISR3         0x13 ; ISR3
@@ -10,6 +10,7 @@
 @let vt_gr_mode_addr 0x17 ; Graphics mode setting address
 
 ; memory segments
+@let charmem_segment 0x0100
 @let stack_segment   0x8000
 @let mmio_segment    0xE000
 @let terminal_addr   0xE000
@@ -37,30 +38,28 @@
   hlt
 
 @label keyboard_isr
-  spu RA                  ; use RA, RB
-  spu RB
-  ldi vt_kb_pp_addr RA    ; RA := 0x17 Keyboard peripheral address pointer
-  ldr RA RA               ; RA := 0xE001 Keyboard peripheral address deref
+  stack_stash RA RB
+  ldi vt_kb_pp_addr RA    ; RA := Keyboard peripheral address pointer
+  ldr RA RA               ; RA := Keyboard peripheral address deref
   ldr RA RA               ; RA := <16-bit keyboard character code> from MMIO register
-  ldi vt_term_pp_addr RB  ; RB := 0x16 Terminal peripheral address pointer
-  ldr RB RB               ; RB := 0xE000 Terminal peripheral address deref
-  str RA RB               ; terminal <- character code
-  spo RB                  ; restore RA, RB
-  spo RA
+  ldi vt_term_pp_addr RB  ; RB := Terminal peripheral address pointer
+  ldr RB RB               ; RB := Terminal peripheral address deref
+  str RA RB               ; terminal <- character code (ASCII?)
+  mov RA RE               ; RE := character code (for debugging)
+  stack_restore RA RB
   rti
 @label program_segment
 
+; define short prelude that sets up vital instructions
+; NOTE: must be shorter than the vector table offset
 @address 0x0
 ; set up stack pointer to point to beginning of stack segment
   ldi vt_stack_addr RA
   ldr RA RF
+  jpi program_segment
+
+@address program_segment
 ; set graphics mode to disabled
-  ldi vt_gr_mode_addr RA
-  ldr RA RA
-  ldi gr_disabled_mode RB
-  str RB RA
+  set_graphics_mode gr_disabled_mode
 ; jump to main (user defined)
   jpi main
-
-@address program_segment
-; set up address for program code
diff --git a/asm/ext_std.py b/asm/ext_std.py
index de7cd43..3d87372 100644
--- a/asm/ext_std.py
+++ b/asm/ext_std.py
@@ -72,9 +72,34 @@ def expand_csi(addr_imm: str):
     *expand_spu("__CSR_SCRATCH"),
     ["jpi", addr_imm]
   ]
+
 def expand_rsr():
   return expand_spo("__CSR_SCRATCH") + [["jpr", "__CSR_SCRATCH"]]
 
+
+def stack_stash(*rs: str):
+  result: ExpandResult = []
+  for r in rs:
+    result += expand_spu(r)
+
+  return result
+
+def stack_restore(*rs: str):
+  result: ExpandResult = []
+  for r in rs:
+    prefix = expand_spu(r)
+    result = prefix + result
+
+  return result
+
+def set_graphics_mode(mode: str):
+  return [
+    ["ldi", "vt_gr_mode_addr", "RA"],
+    ["ldr", "RA", "RA"],
+    ["ldi", mode, "RB"],
+    ["str", "RB", "RA"],
+  ]
+
 expansions: OpExpansionDict = {
   "add": expand_add,
   "sub": expand_sub,
@@ -98,4 +123,7 @@ expansions: OpExpansionDict = {
   "csr": expand_csr,
   "csi": expand_csi,
   "rsr": expand_rsr,
+  "stack_stash": stack_stash,
+  "stack_restore": stack_restore,
+  "set_graphics_mode": set_graphics_mode,
 }
diff --git a/asm/text_mode.atk16 b/asm/text_mode.atk16
index 05b4fd3..f7bc40f 100644
--- a/asm/text_mode.atk16
+++ b/asm/text_mode.atk16
@@ -7,11 +7,9 @@
 @include bootstrap
 
 @label main
-  ; set graphics mode to gr_text_mode
-  ldi vt_gr_mode_addr RA
-  ldr RA RA
-  ldi gr_text_mode RB
-  str RB RA
+  ; set graphics mode to sprite mode
+  set_graphics_mode gr_sprite_mode
+  ; set_graphics_mode gr_text_mode
 
 @label loop
   jpi loop