diff --git a/asm/link_rfu.s b/asm/link_rfu.s
index b5b7a43f2..7d8c8b2b1 100644
--- a/asm/link_rfu.s
+++ b/asm/link_rfu.s
@@ -5,123 +5,6 @@
 
 	.text
 
-	thumb_func_start sub_800C12C
-sub_800C12C: @ 800C12C
-	push {r4-r7,lr}
-	mov r7, r8
-	push {r7}
-	lsls r0, 16
-	lsrs r6, r0, 16
-	lsls r1, 16
-	lsrs r1, 16
-	mov r8, r1
-	ldr r1, =gUnknown_03004140
-	ldrb r0, [r1, 0x4]
-	cmp r0, 0
-	beq _0800C164
-	subs r0, 0x9
-	lsls r0, 24
-	lsrs r0, 24
-	cmp r0, 0x2
-	bls _0800C164
-	movs r0, 0x1
-	strh r0, [r1, 0x14]
-	movs r0, 0xF3
-	movs r1, 0x1
-	bl sub_800D30C
-	movs r0, 0x1
-	b _0800C204
-	.pool
-_0800C164:
-	bl rfu_getMasterSlave
-	lsls r0, 24
-	cmp r0, 0
-	bne _0800C184
-	ldr r1, =gUnknown_03004140
-	movs r0, 0x2
-	strh r0, [r1, 0x14]
-	movs r0, 0xF3
-	movs r1, 0x1
-	bl sub_800D30C
-	movs r0, 0x2
-	b _0800C204
-	.pool
-_0800C184:
-	movs r2, 0
-	ldr r0, =gUnknown_03007890
-	ldr r1, [r0]
-	ldrb r3, [r1, 0x8]
-	ldr r5, =gUnknown_03004140
-	adds r7, r0, 0
-	cmp r2, r3
-	bcs _0800C1B2
-	ldrh r0, [r1, 0x14]
-	cmp r0, r6
-	beq _0800C1B2
-	adds r4, r1, 0
-	adds r1, r3, 0
-_0800C19E:
-	adds r0, r2, 0x1
-	lsls r0, 24
-	lsrs r2, r0, 24
-	cmp r2, r1
-	bcs _0800C1B2
-	lsls r0, r2, 5
-	adds r0, r4, r0
-	ldrh r0, [r0, 0x14]
-	cmp r0, r6
-	bne _0800C19E
-_0800C1B2:
-	ldr r0, [r7]
-	ldrb r0, [r0, 0x8]
-	cmp r0, 0
-	beq _0800C1BE
-	cmp r2, r0
-	bne _0800C1D8
-_0800C1BE:
-	movs r0, 0x3
-	strh r0, [r5, 0x14]
-	movs r0, 0xF3
-	movs r1, 0x1
-	bl sub_800D30C
-	movs r0, 0x3
-	b _0800C204
-	.pool
-_0800C1D8:
-	ldrb r0, [r5, 0x4]
-	cmp r0, 0
-	beq _0800C1E2
-	cmp r0, 0x9
-	bne _0800C1EA
-_0800C1E2:
-	movs r0, 0xC
-	strb r0, [r5, 0x4]
-	movs r0, 0xD
-	b _0800C1F0
-_0800C1EA:
-	movs r0, 0xB
-	strb r0, [r5, 0x4]
-	movs r0, 0xC
-_0800C1F0:
-	strb r0, [r5, 0x5]
-	strh r6, [r5, 0x1E]
-	mov r0, r8
-	strh r0, [r5, 0x1A]
-	ldrb r0, [r5, 0x7]
-	cmp r0, 0
-	beq _0800C202
-	movs r0, 0x7
-	strb r0, [r5, 0x7]
-_0800C202:
-	movs r0, 0
-_0800C204:
-	pop {r3}
-	mov r8, r3
-	pop {r4-r7}
-	pop {r1}
-	bx r1
-	thumb_func_end sub_800C12C
-
 	thumb_func_start sub_800C210
 sub_800C210: @ 800C210
 	push {r4-r7,lr}
diff --git a/include/librfu.h b/include/librfu.h
index 3d1970437..481845f09 100644
--- a/include/librfu.h
+++ b/include/librfu.h
@@ -130,6 +130,13 @@ struct RfuUnk3
 struct RfuUnk5
 {
     u8 unk_00;
+    u8 filler_01[2];
+    u8 unk_03;
+    u8 filler_04[4];
+    u8 unk_08;
+    u8 filler_09[11];
+    u16 unk_14;
+    u8 filler_16[10];
 };
 
 extern struct RfuStruct *gRfuState;
diff --git a/include/link_rfu.h b/include/link_rfu.h
index f64c74f6b..64510c1c6 100644
--- a/include/link_rfu.h
+++ b/include/link_rfu.h
@@ -53,7 +53,8 @@ struct UnkRfuStruct_1 {
     u8 filler_16[2];
     u16 unk_18;
     u16 unk_1a;
-    u8 filler_1c[4];
+    u8 filler_1c[2];
+    u16 unk_1e;
     u16 *unk_20;
     u8 unk_24;
     u16 unk_26;
diff --git a/src/librfu_rfu.c b/src/librfu_rfu.c
index 2169f4578..c5aa25c10 100644
--- a/src/librfu_rfu.c
+++ b/src/librfu_rfu.c
@@ -3,14 +3,6 @@
 
 #include "librfu.h"
 
-extern struct RfuUnk5 *gUnknown_03007890;
-extern u32 *gUnknown_03007894;
-extern struct RfuUnk3* gUnknown_03007898;
-extern struct RfuUnk2* gUnknown_03007880[4];
-extern struct RfuUnk1* gUnknown_03007870[4];
-extern void* sub_82E53F4;
-extern void rfu_STC_clearAPIVariables(void);
-
 // Nonmatching, only register differences
 /*u16 rfu_initializeAPI(u32 *unk0, u16 unk1, IntrFunc *interrupt, bool8 copyInterruptToRam)
 {
diff --git a/src/link_rfu.c b/src/link_rfu.c
index b7b36db2a..8d81cddc4 100644
--- a/src/link_rfu.c
+++ b/src/link_rfu.c
@@ -191,3 +191,53 @@ u8 sub_800C054(u8 r5, u16 r7, u16 r8, u16 *r6)
     gUnknown_03004140.unk_20 = r6;
     return 0;
 }
+
+u8 sub_800C12C(u16 r6, u16 r8)
+{
+    u8 i;
+    struct RfuUnk5 *tmp;
+
+    if (gUnknown_03004140.unk_04 != 0 && (gUnknown_03004140.unk_04 < 9 || gUnknown_03004140.unk_04 > 11))
+    {
+        gUnknown_03004140.unk_14 = 1;
+        sub_800D30C(0xF3, 0x01);
+        return 1;
+    }
+    if (!rfu_getMasterSlave())
+    {
+        gUnknown_03004140.unk_14 = 2;
+        sub_800D30C(0xF3, 0x01);
+        return 2;
+    }
+    for (i = 0; i < gUnknown_03007890->unk_08; i ++)
+    {
+        tmp = &gUnknown_03007890[i];
+        if (tmp->unk_14 == r6)
+        {
+            break;
+        }
+    }
+    if (gUnknown_03007890->unk_08 == 0 || i == gUnknown_03007890->unk_08)
+    {
+        gUnknown_03004140.unk_14 = 3;
+        sub_800D30C(0xF3, 0x01);
+        return 3;
+    }
+    if (gUnknown_03004140.unk_04 == 0 || gUnknown_03004140.unk_04 == 9)
+    {
+        gUnknown_03004140.unk_04 = 12;
+        gUnknown_03004140.unk_05 = 13;
+    }
+    else
+    {
+        gUnknown_03004140.unk_04 = 11;
+        gUnknown_03004140.unk_05 = 12;
+    }
+    gUnknown_03004140.unk_1e = r6;
+    gUnknown_03004140.unk_1a = r8;
+    if (gUnknown_03004140.unk_07 != 0)
+    {
+        gUnknown_03004140.unk_07 = 7;
+    }
+    return 0;
+}