diff --git a/engine/battle/checkbattlescene.asm b/engine/battle/checkbattlescene.asm
index 24d06b8c9..a33cc62e3 100644
--- a/engine/battle/checkbattlescene.asm
+++ b/engine/battle/checkbattlescene.asm
@@ -21,7 +21,7 @@ CheckBattleScene: ; 4ea44
 
 	ld a, 4 ; MBC30 bank used by JP Crystal; inaccessible by MBC3
 	call GetSRAMBank
-	ld a, [$a60c]
+	ld a, [$a60c] ; address of MBC30 bank
 	ld c, a
 	call CloseSRAM
 
diff --git a/engine/battle/core.asm b/engine/battle/core.asm
index 7649eba84..6d4401946 100644
--- a/engine/battle/core.asm
+++ b/engine/battle/core.asm
@@ -234,7 +234,7 @@ BattleTurn: ; 3c12f
 MobileFn_3c1bf: mobile
 	ld a, 5 ; MBC30 bank used by JP Crystal; inaccessible by MBC3
 	call GetSRAMBank
-	ld hl, $a89b ; s5_a89b
+	ld hl, $a89b ; address of MBC30 bank
 	inc [hl]
 	jr nz, .finish
 	dec hl
diff --git a/engine/mystery_gift.asm b/engine/mystery_gift.asm
index 9a8c41f91..ec5cdecab 100755
--- a/engine/mystery_gift.asm
+++ b/engine/mystery_gift.asm
@@ -1563,10 +1563,10 @@ Function10578c: ; 10578c (41:578c)
 	inc de
 	ld a, 4 ; MBC30 bank used by JP Crystal; inaccessible by MBC3
 	call GetSRAMBank
-	ld hl, $a603
+	ld hl, $a603 ; address of MBC30 bank
 	ld bc, $8
 	call CopyBytes
-	ld hl, $a007
+	ld hl, $a007 ; address of MBC30 bank
 	ld bc, $c
 	call CopyBytes
 	call CloseSRAM
diff --git a/engine/rtc.asm b/engine/rtc.asm
index bed0fcda4..b44db1c7c 100755
--- a/engine/rtc.asm
+++ b/engine/rtc.asm
@@ -148,12 +148,12 @@ Function140ae: ; 140ae
 ; mobile
 	ld a, 5 ; MBC30 bank used by JP Crystal; inaccessible by MBC3
 	call GetSRAMBank
-	ld a, [$aa8c]
+	ld a, [$aa8c] ; address of MBC30 bank
 	inc a
-	ld [$aa8c], a
-	ld a, [$b2fa]
+	ld [$aa8c], a ; address of MBC30 bank
+	ld a, [$b2fa] ; address of MBC30 bank
 	inc a
-	ld [$b2fa], a
+	ld [$b2fa], a ; address of MBC30 bank
 	call CloseSRAM
 	ret
 
diff --git a/engine/save.asm b/engine/save.asm
index a869d903e..12e5964b9 100644
--- a/engine/save.asm
+++ b/engine/save.asm
@@ -421,7 +421,7 @@ Function14d18: ; 14d18
 	ld a, 4 ; MBC30 bank used by JP Crystal; inaccessible by MBC3
 	call GetSRAMBank
 	ld hl, .Data
-	ld de, $a007
+	ld de, $a007 ; address of MBC30 bank
 	ld bc, .DataEnd - .Data
 	call CopyBytes
 	jp CloseSRAM
@@ -456,7 +456,7 @@ Function14d6c: ; 14d6c
 ; XXX
 	ld a, 4 ; MBC30 bank used by JP Crystal; inaccessible by MBC3
 	call GetSRAMBank
-	ld a, [$a60b]
+	ld a, [$a60b] ; address of MBC30 bank
 	ld b, $0
 	and a
 	jr z, .ok
@@ -464,7 +464,7 @@ Function14d6c: ; 14d6c
 
 .ok
 	ld a, b
-	ld [$a60b], a
+	ld [$a60b], a ; address of MBC30 bank
 	call CloseSRAM
 	ret
 ; 14d83
@@ -474,8 +474,8 @@ Function14d83: ; 14d83
 	ld a, 4 ; MBC30 bank used by JP Crystal; inaccessible by MBC3
 	call GetSRAMBank
 	xor a
-	ld [$a60c], a
-	ld [$a60d], a
+	ld [$a60c], a ; address of MBC30 bank
+	ld [$a60d], a ; address of MBC30 bank
 	call CloseSRAM
 	ret
 ; 14d93
@@ -485,7 +485,7 @@ Function14d93: ; 14d93
 	ld a, 7 ; MBC30 bank used by JP Crystal; inaccessible by MBC3
 	call GetSRAMBank
 	xor a
-	ld [$a000], a
+	ld [$a000], a ; address of MBC30 bank
 	call CloseSRAM
 	ret
 ; 14da0
@@ -873,6 +873,11 @@ VerifyBackupChecksum: ; 1507c (5:507c)
 
 
 _SaveData: ; 1509a
+	; This is called within two scenarios:
+	;   a) ErasePreviousSave (the process of erasing the save from a previous game file)
+	;   b) unused mobile functionality
+	; It is not part of a regular save.
+	
 	ld a, BANK(sCrystalData)
 	call GetSRAMBank
 	ld hl, wCrystalData
@@ -880,7 +885,11 @@ _SaveData: ; 1509a
 	ld bc, wCrystalDataEnd - wCrystalData
 	call CopyBytes
 
-	; XXX SRAM bank 7
+	; This block originally had some mobile functionality, but since we're still in
+	; BANK(sCrystalData), it instead overwrites the sixteen EventFlags starting at 1:a603 with
+	; garbage from wd479. This isn't an issue, since ErasePreviousSave is followed by a regular
+	; save that unwrites the garbage.
+	
 	ld hl, wd479
 	ld a, [hli]
 	ld [$a60e + 0], a
@@ -897,8 +906,10 @@ _LoadData: ; 150b9
 	ld de, wCrystalData
 	ld bc, wCrystalDataEnd - wCrystalData
 	call CopyBytes
-
-	; XXX SRAM bank 7
+	
+	; This block originally had some mobile functionality to mirror _SaveData above, but instead it
+	; (harmlessly) writes the aforementioned EventFlags to the unused wd479.
+	
 	ld hl, wd479
 	ld a, [$a60e + 0]
 	ld [hli], a