1 files changed, 58 insertions, 0 deletions
diff --git a/data/rambasic.asm b/data/rambasic.asm
new file mode 100644
index 0000000..3b7323f
--- /dev/null
+++ b/data/rambasic.asm
@@ -0,0 +1,58 @@
+; This code must be position-independent.
+
+	org 0
+entry:				; On entry HL points here
+	inc h			; Buffer at +256 bytes
+	push hl			; Buffer address
+	xor a
+	ld l,a
+	ld h,a
+	; DE -> ROM address
+	
+	; Wait for NMI before copying the first chunk
+	di
+	halt
+
+	; Test for RAM
+	inc a			; A = 1
+	out (7),a
+	ld c,(hl)
+	add c
+	ld (hl),a
+	ld a,(hl)
+	sub c
+	jr z,error		; A = 0, HL = 0 on error
+
+copy:
+	xor a
+	out (7),a
+
+	; Copy to buffer
+	pop de			; Buffer address
+	push de			; Buffer address
+	push hl			; ROM address
+	ld bc,256
+	ldir
+
+	inc a			; A = 1
+	out (7),a
+
+	; Copy from buffer
+	pop de			; ROM address
+	pop hl			; Buffer address
+	push hl			; Buffer address
+	inc b			; BC <- 256
+	ldir
+
+	ex de,hl		; ROM address -> HL
+
+	bit 7,h
+	jr z,copy
+
+	; A = 1, HL != 0
+
+error:
+	out (7),a
+	ei
+
+	ret