diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6e1c60b98c..75318a55ec 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,7 @@ All notable changes to this project will be documented in this file.
 This project uses the changelog in accordance with [keepchangelog](http://keepachangelog.com/). Please use this to write notable changes, which is not the same as git commit log...
 
 ## [unreleased][unreleased]
+- Changed (extended) area accessible by spiffs into last page of FLASH (@piotrva)
 - Changed flash-stored key dictionaries (Mifare, iClass, T55XX) and T55XX configurations to SPIFFS files (@piotrva)
 - Changed `lf em 410x sim` to use default gap value of 0 and extended help (@piotrva)
 - Changed `hf 14a info` - now identifies MIAFRE Duox (@iceman1001)
diff --git a/armsrc/spiffs_config.h b/armsrc/spiffs_config.h
index 4f8a5dd26c..d0d4eb1d71 100644
--- a/armsrc/spiffs_config.h
+++ b/armsrc/spiffs_config.h
@@ -28,6 +28,7 @@
 #include "printf.h"
 #include "string.h"
 #include "flashmem.h"
+#include "pmflash.h"
 
 //#include <stddef.h>
 //#include <unistd.h>
@@ -236,7 +237,7 @@ typedef uint8_t u8_t;
 // Instead of giving parameters in config struct, singleton build must
 // give parameters in defines below.
 #ifndef SPIFFS_CFG_PHYS_SZ
-#define SPIFFS_CFG_PHYS_SZ(ignore)        (1024 * 64 * (spi_flash_pages64k - 1))
+#define SPIFFS_CFG_PHYS_SZ(ignore)        ((1024 * 64 * spi_flash_pages64k) - (1024 * 4 * (FLASH_RESERVED_TRAILING_4K_SECTORS + 1)))
 #endif
 #ifndef SPIFFS_CFG_PHYS_ERASE_SZ
 #define SPIFFS_CFG_PHYS_ERASE_SZ(ignore)  (4*1024)
diff --git a/client/src/scripting.c b/client/src/scripting.c
index 0657ae8d67..4f7705eb3f 100644
--- a/client/src/scripting.c
+++ b/client/src/scripting.c
@@ -283,7 +283,7 @@ static int l_GetFromFlashMemSpiffs(lua_State *L) {
         return returnToLuaWithError(L, "No FLASH MEM support");
     }
 
-    uint32_t start_index = 0, len = 0x40000; //FLASH_MEM_MAX_SIZE
+    uint32_t start_index = 0, len = 0x40000;  // 256KB FLASH_MEM_MAX_SIZE as default value
     char destfilename[32] = {0};
     size_t size;
 
diff --git a/doc/ext_flash_notes.md b/doc/ext_flash_notes.md
index d54c2be538..25ba2be14c 100644
--- a/doc/ext_flash_notes.md
+++ b/doc/ext_flash_notes.md
@@ -19,7 +19,7 @@ External 256kbytes flash is a unique feature of the RDV4 edition.
 
 Flash memory is
 
-* 256KB (0x40000= 262144)
+* 256KB (0x40000 = 262144)
 * divided into 4 pages of 64KB (0x10000 = 65536)
 * 4 pages divided into 16 sectors of 4KB (0x1000 = 4096), so last sector is at 0x3F000
 
@@ -31,6 +31,8 @@ Therefore a flash address can be interpreted as such:
     ^^^ offset         ^^^ offset 0xF7F
 ```
 
+Please note that for other flash memory sizes than 256KB a "Page 3" will be the last page of the memory, and address offsets would be dependant on the memory size.
+
 ## Layout
 ^[Top](#top)
 
@@ -49,7 +51,7 @@ Page 2:
 * to dump it: `mem dump -f page2_dump -o 131072 -l 65536`
 * to erase it: `mem wipe -p 2`
 
-Page 3:
+Page 3 (or the last page for memories other than 256KB):
 * used by Proxmark3 RDV4 specific functions: flash signature, see below for details
 * to dump it: `mem dump -f page3_dump -o 196608 -l 65536`
 * to erase it:
@@ -60,13 +62,19 @@ Page 3:
 ## Page3 Layout
 ^[Top](#top)
 
-Page3 is used as follows by the Proxmark3 RDV4 firmware:
+Page3 (or the last page for memories other than 256KB) is used as follows by the Proxmark3 RDV4 firmware:
 
 * **RSA SIGNATURE**, see below for details
   * offset: page 3 sector 15 (0xF) offset 0xF7F @ 3*0x10000+15*0x1000+0xF7F=0x3FF7F  (decimal 262015)
   * length: 128 bytes
   * offset should have been 0x3FF80 but historically it's one byte off and therefore the last byte of the flash is unused
 
+* **Reserved for future use**
+  * offset: page 3 sector 14 (0xE)
+
+* **SPIFFS sectors**
+  * offset: page 3 sectors 13..0 (0xD..0x0)
+
 ## RSA signature
 ^[Top](#top)
 
diff --git a/include/pmflash.h b/include/pmflash.h
index 67f5b350a3..7820ad4e2e 100644
--- a/include/pmflash.h
+++ b/include/pmflash.h
@@ -22,29 +22,32 @@
 #include "common.h"
 
 // RDV40 Section
-// 256kb divided into 4k sectors.
-//
-// 0x3F000 - 1 4kb sector = signature
-// 0x3E000 - 1 4kb sector = settings
+// 256KB divided into 4K sectors.
+// +--------+-------------+---------+--------------------------+
+// | Sector | 256KB addr* |  Size   | Description              |
+// +--------+-------------+---------+--------------------------+
+// | N      |   0x3F000   | 1 * 4KB | signature                |
+// | N-1    |   0x3E000   | 1 * 4KB | reserved for future use  |
+// +--------+-------------+---------+--------------------------+
 //
+// * For different memory size than 256KB the address is not valid.
+//   Please instead refer to Sector number, where N is the last
+//   4KB secotr of the memory in question.
+
 #ifndef FLASH_MEM_BLOCK_SIZE
 # define FLASH_MEM_BLOCK_SIZE   256
 #endif
 
-#ifndef FLASH_MEM_MAX_SIZE
-# define FLASH_MEM_MAX_SIZE     0x40000  // (262144)
-#endif
 #ifndef FLASH_MEM_MAX_SIZE_P
 # define FLASH_MEM_MAX_SIZE_P(p64k) (1024 * 64 * (p64k))
 #endif
 
-#ifndef FLASH_MEM_MAX_4K_SECTOR
-# define FLASH_MEM_MAX_4K_SECTOR   0x3F000
-#endif
 #ifndef FLASH_MEM_MAX_4K_SECTOR_P
 # define FLASH_MEM_MAX_4K_SECTOR_P(p64k)  (FLASH_MEM_MAX_SIZE_P(p64k) - 4096)
 #endif
 
+#define FLASH_RESERVED_TRAILING_4K_SECTORS 2
+
 #ifndef FLASH_MEM_ID_LEN
 # define FLASH_MEM_ID_LEN 8
 #endif
@@ -53,10 +56,7 @@
 # define FLASH_MEM_SIGNATURE_LEN 128
 #endif
 
-#ifndef FLASH_MEM_SIGNATURE_OFFSET
 // -1 for historical compatibility with already released Proxmark3 RDV4.0 devices
-# define FLASH_MEM_SIGNATURE_OFFSET (FLASH_MEM_MAX_SIZE - FLASH_MEM_SIGNATURE_LEN - 1)
-#endif
 #ifndef FLASH_MEM_SIGNATURE_OFFSET_P
 # define FLASH_MEM_SIGNATURE_OFFSET_P(p64k) (FLASH_MEM_MAX_SIZE_P(p64k) - FLASH_MEM_SIGNATURE_LEN - 1)
 #endif