From 83aef192e447c800cba6f4dbde8a450a4f8581a5 Mon Sep 17 00:00:00 2001
From: Jacques Comeaux <jacquesrcomeaux@protonmail.com>
Date: Mon, 1 Jul 2024 12:16:02 -0500
Subject: Use in-house CRC32 computation for boot sector

---
 misc/crc.s | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)
 create mode 100644 misc/crc.s

(limited to 'misc/crc.s')

diff --git a/misc/crc.s b/misc/crc.s
new file mode 100644
index 0000000..03c0ce2
--- /dev/null
+++ b/misc/crc.s
@@ -0,0 +1,24 @@
+.syntax unified
+.cpu cortex-m0plus
+.thumb
+
+.type CRC32, %function
+.global CRC32
+
+// R0 = input addr
+// R1 = length
+CRC32:  LDR R5, =0x04C11DB7
+        LDR R4, =0xFFFFFFFF
+10:     LDR R2, [R0]
+        REV R2, R2;
+        EORS R4, R2
+        MOVS R3, 32
+20:     LSLS R4, 1
+        BCC 30f
+        EORS R4, R5
+30:     SUBS R3, 1
+        BNE 20b
+        ADDS R0, 4
+        SUBS R1, 1
+        BNE 10b
+        BX LR
-- 
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