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(define addr-segment-heap #x8000) ; grows up until SP
(define addr-segment-mmio #xE7F0)
(define addr-segment-sprite #xE800)
(define addr-segment-text #xF800)
;; note: sprite memory & text memory can overlap
;; since they are never used at the same time
(define addr-mmio-terminal (+ addr-segment-mmio 0))
(define addr-mmio-keyboard (+ addr-segment-mmio 1))
(define addr-mmio-graphics-mode (+ addr-segment-mmio 2))
(define graphics-disabled 0)
(define graphics-text 1)
(define graphics-sprite 2)
(at-addr #x0)
(def-label 'entrypoint
;; Set stack pointer to end of heap segment, i.e. one below addr-segment-mmio.
;; Stack grows down.
;; Heap grows up from addr-segment-heap until it meets the stack.
(ld SP (u16 (- addr-segment-mmio 1)))
;; Set graphics mode to disabled.
(ld R0 (u16 addr-mmio-graphics-mode))
(st R0 (u16 graphics-disabled)))
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