Differences

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--- notes:flashcart:r4ds [2023/10/16 13:51] – asie
+++ notes:flashcart:r4ds [2023/10/16 15:03] (current) – asie
@@ Line 1: / Line 1: @@
 ====== R4 (NDS) programming ======
-Original research provided mostly by lifehackerhansol.
+Original research provided mostly [[https://github.com/DS-Homebrew/DLDI/wiki/Original-R4-and-M3-Simply|by lifehackerhansol]].
 ===== Control flags =====
@@ Line 13: / Line 13: @@
 ===== Commands =====
-==== Get card status (B0 ?? ?? ?? ?? ?? ?? ??) ====
+==== Get card status (B0 00 00 00 00 00 00 00) ====
 <code>
                  bit                 0
- ???? ???? ???? ???? ???? ???? ???? ?sss
+ ???? ???? ???? ???? ???? ???L LLml lsss
-                                     |||
+                             | |||| ||||
-                                     +++- Initialization status:
+                             | |||| |+++- Initialization status:
-- (in progress)
+                             | |||| |      0 - (in progress)
-- SD/TF card not found
+                             | |||| |      1 - SD/TF card not found
-- SD/TF card read error
+                             | |||| |      2 - SD/TF card read error
-- could not find _DS_MENU.DAT
+                             | |||| |      3 - could not find _DS_MENU.DAT
-- success
+                             | |||| |      4 - success
+                             | |||+-+---- Language:
+                             | |||         1 - Japanese
+                             | |||         2 - English
+                             | |||         3 - Chinese
+                             | ||+------- Model:
+                             | ||          0 - M3DS Simply
+                             | ||          1 - R4 Revolution for DS
+                             +-++-------- Sub-language:
+:2  - French
+:4  - Korean
+:0? - Simplified Chinese
+:1? - Traditional Chinese
 </code>
-==== Save read request (B2 sd sc sb sa ?? ?? ??) ====
+==== Save read request (B2 sd sc sb sa 00 00 00) ====
 SD read request, but using the "save" FAT entry table.
-==== Save read data (B3 ?? ?? ?? ?? ?? ?? ??) ====
+==== Save read data (B3 00 00 00 00 00 00 00) ====
 SD read data, but using the "save" FAT entry table.
@@ Line 51: / Line 62: @@
 </code>
-==== ROM read request (B6 ?? ?? ?? ?? ?? ?? ??) ====
+==== ROM read request (B6 sd sc sb sa 00 00 00) ====
 SD read request, but using the "ROM" FAT entry table.
@@ Line 57: / Line 68: @@
 Points to _DS_MENU.DAT on initialization.
-==== ROM read data (B7 ad ac ab aa ?? ?? ??) ====
+==== ROM read data (B7 00 00 00 00 00 00 00) ====
 SD read data, but using the "ROM" FAT entry table.
-==== ? Get card ID ? (B8 ?? ?? ?? ?? ?? ?? ??) ====
+==== Get card ID (B8 00 00 00 00 00 00 00) ====
+[[https://github.com/DS-Homebrew/DLDI/wiki/Original-R4-and-M3-Simply#original-r4--m3-ds-simply|Quoting lifehackerhansol]]:
+> Card ID commands are not patched and use the timings from the retail game ROM header, but without L1 latency (that's what the SDK does). Those can be as fast as a single cycle of L2 latency, depending on the game.
 ==== SD read request (B9 sd sc sb sa 00 00 00) ====
@@ Line 67: / Line 82: @@
   * (MSB) sd sc sb sa (LSB) - sector address, in bytes
-Returns zero when data is ready to access, non-zero if ongoing.
+Returns ''0x00000000'' when data is ready to access, ''0x00000001'' if ongoing.
 ==== SD read data (BA 00 00 00 00 00 00 00) ====
@@ Line 83: / Line 98: @@
   * (MSB) sd sc sb sa (LSB) - sector address, in bytes
-Returns zero if done, non-zero if ongoing.
+Returns ''0x00000000'' when data is ready to access, ''0x00000001'' if ongoing.
-==== Save write start (BD ?? ?? ?? ?? ?? ?? ??) ====
+==== Save write start (BD sd sc sb sa 00 00 00) ====
 SD write start, but using the "save" FAT entry table.
-==== Save write status (BE ?? ?? ?? ?? ?? ?? ??) ====
+==== Save write status (BE sd sc sb sa 00 00 00) ====
 SD write status, but using the "save" FAT entry table.
-==== ROM read decrypted data (BF ?? ?? ?? ?? ?? ?? ??) ====
+==== ROM read decrypted data (BF 00 00 00 00 00 00 00) ====
 Same as SD read data, but applying a XOR-based obfuscation algorithm to the buffer's contents.
@@ Line 102: / Line 117: @@
 <code>
-    uint8_t[512] in;
+uint8_t[512] in;
-    uint8_t[512] out;
+uint8_t[512] out;
-    uint16_t key1 = key ^ currentSector;
+uint16_t key1 = key ^ currentSector;
-    for (int i = 0; i < 512; i++)
+for (int i = 0; i < 512; i++)
-    {
+{
-        // Derive key2 from key1.
+    // Derive key2 from key1.
-        uint8_t key2 = ((key1 >> 7) & 0x80)
+    uint8_t key2 = ((key1 >> 7) & 0x80)
-            | ((key1 >> 6) & 0x60)
+        | ((key1 >> 6) & 0x60)
-            | ((key1 >> 5) & 0x10)
+        | ((key1 >> 5) & 0x10)
-            | ((key1 >> 4) & 0x0C)
+        | ((key1 >> 4) & 0x0C)
-            | (key1 & 0x03);
+        | (key1 & 0x03);
-        // Decrypt byte.
+    // Decrypt byte.
-        dest[i] = src[i] ^ key2;
+    dest[i] = src[i] ^ key2;
-        // Derive next key1 from key2.
+    // Derive next key1 from key2.
-        uint16_t tmp = ((src[i] << 8) ^ key1);
+    uint16_t tmp = ((src[i] << 8) ^ key1);
-        uint16_t tmpXor = 0;
+    uint16_t tmpXor = 0;
-        for (int ii = 0; ii < 16; ii++)
+    for (int ii = 0; ii < 16; ii++)
-            tmpXor ^= (tmp >> ii);
+        tmpXor ^= (tmp >> ii);
-        uint16_t newKey1 = 0;
+    uint16_t newKey1 = 0;
-        newKey1 |= ((tmpXor & 0x80) | (tmp & 0x7C)) << 8;
+    newKey1 |= ((tmpXor & 0x80) | (tmp & 0x7C)) << 8;
-        newKey1 |= ((tmp ^ (tmpXor >> 14)) << 8) & 0x0300;
+    newKey1 |= ((tmp ^ (tmpXor >> 14)) << 8) & 0x0300;
-        newKey1 |= (((tmp >> 1) ^ tmp) >> 6) & 0xFC;
+    newKey1 |= (((tmp >> 1) ^ tmp) >> 6) & 0xFC;
-        newKey1 |= ((tmp ^ (tmpXor >> 1)) >> 8) & 0x03;
+    newKey1 |= ((tmp ^ (tmpXor >> 1)) >> 8) & 0x03;
-        key1 = newKey1;
+    key1 = newKey1;
-    }
 }
 </code>