From: Lukas Krickl <lukas@krickl.dev>
Date: Sun, 1 Feb 2026 07:38:06 +0000 (+0100)
Subject: math: Added 16 bit sub
X-Git-Url: https://git.krickl.dev/?a=commitdiff_plain;h=9b8e9767f1a20190412bcdb5381dd6aa24a9fffd;p=gbrg%2F.git

math: Added 16 bit sub
---

diff --git a/src/math.s b/src/math.s
index 22e0f64..6a612ee 100644
--- a/src/math.s
+++ b/src/math.s
@@ -52,4 +52,19 @@ m16_add:
 	;	returns:
 	;		m16_a: m16_a - m16_b
 m16_sub:
+	ld a, [m16_b]
+	ld b, a
+	ld a, [m16_a]
+	
+	; low is stored
+	sub a, b
+	ld [m16_a], a
+
+	ld a, [m16_b+1]
+	ld b, a
+	ld a, [m16_a+1]
+
+	; high + carry stored
+	sbc a, b
+	ld [m16_a+1], a
 	ret