From cc8a9fc95fb1e73887c0e90b90e3f14f17ba20da Mon Sep 17 00:00:00 2001
From: Gale Faraday <k4mu1kazum4@gmail.com>
Date: Tue, 2 Sep 2025 16:46:45 -0500
Subject: [PATCH] feat(boot): new stack initialization routine

---
 code/boot/src/hardware.inc | 10 ++++++++++
 code/boot/src/reset.s      | 20 +++++++++++++++++---
 2 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/code/boot/src/hardware.inc b/code/boot/src/hardware.inc
index fcbe629..01e96b1 100644
--- a/code/boot/src/hardware.inc
+++ b/code/boot/src/hardware.inc
@@ -15,6 +15,16 @@ UART_BASE EQU $7F00 ; UART Base Address
 ROM_BASE  EQU $8000 ; ROM Base Address and Entry Point
 VECS_BASE EQU $FFF0 ; Vectors Base Address
 
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;;
+;; Stack Base Address and Size Information
+;;
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+STACK_BOTTOM EQU $0100 ; Bottom address of system stack
+STACK_DEPTH  EQU $FF   ; System stack's depth
+STACK_TOP    EQU STACK_BOTTOM+STACK_DEPTH ; Top address of system stack
+
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;
 ;; UART Registers and Flags
diff --git a/code/boot/src/reset.s b/code/boot/src/reset.s
index 32a96a1..afc3c4b 100644
--- a/code/boot/src/reset.s
+++ b/code/boot/src/reset.s
@@ -16,8 +16,21 @@
   EXPORT RESET
 
 RESET
+
+CLRSTACK
+  ; Initialize the system stack
+  lda #$00           ; Initialize A & X to zero out the stack
+  ldx #$0000
+NEXT@
+  sta STACK_BOTTOM,x ; Write a zero and progress to the next byte
+  leax 1,x
+  cmpx #STACK_DEPTH  ; See if we're at the top of the stack yet
+  blo NEXT@          ; Loop if we aren't at the end yet
+  lds STACK_TOP      ; Set S to top of newly cleared stack
+
+SERINIT
   ; 8n1 Serial Enable DLAB
-  lda #UARTF_LCR_WLS | UARTF_LCR_DLAB
+  lda #UARTF_LCR_WLS|UARTF_LCR_DLAB
   sta UART_LCR
   ; REVIEW: Potential endianness hiccough here
   ldd #$0C00           ; Set divisor to 12 (9600 baud)
@@ -29,7 +42,8 @@ RESET
   sta UART_MCR
   lda #'H               ; send 'H'
   sta UART_BUFR
-WAIT@
+
+WAIT
   sync                 ; Wait for interrupts
   nop
-  bra WAIT@
+  bra WAIT