diff --git a/embed/boardloader/main.c b/embed/boardloader/main.c
index 4ecd1153e..fc16f02e5 100644
--- a/embed/boardloader/main.c
+++ b/embed/boardloader/main.c
@@ -125,7 +125,7 @@ static secbool copy_sdcard(void)
     for (int i = 0; i < (IMAGE_HEADER_SIZE + codelen) / SDCARD_BLOCK_SIZE; i++) {
         ensure(sdcard_read_blocks(buf, i, 1), NULL);
         for (int j = 0; j < SDCARD_BLOCK_SIZE / sizeof(uint32_t); j++) {
-            ensure(flash_write_word(BOOTLOADER_START + i * SDCARD_BLOCK_SIZE + j * sizeof(uint32_t), buf[j]), NULL);
+            ensure(flash_write_word(FLASH_SECTOR_BOOTLOADER, i * SDCARD_BLOCK_SIZE + j * sizeof(uint32_t), buf[j]), NULL);
         }
     }
 
diff --git a/embed/bootloader/messages.c b/embed/bootloader/messages.c
index fdbc09bc9..0f0e87875 100644
--- a/embed/bootloader/messages.c
+++ b/embed/bootloader/messages.c
@@ -440,7 +440,7 @@ int process_msg_FirmwareUpload(uint8_t iface_num, uint32_t msg_size, uint8_t *bu
 
     const uint32_t * const src = (const uint32_t * const)chunk_buffer;
     for (int i = 0; i < chunk_size / sizeof(uint32_t); i++) {
-        ensure(flash_write_word_rel(firmware_sectors[firmware_block], i * sizeof(uint32_t), src[i]), NULL);
+        ensure(flash_write_word(firmware_sectors[firmware_block], i * sizeof(uint32_t), src[i]), NULL);
     }
 
     ensure(flash_lock(), NULL);
diff --git a/embed/extmod/modtrezorconfig/norcow.c b/embed/extmod/modtrezorconfig/norcow.c
index 767af5591..6839d7948 100644
--- a/embed/extmod/modtrezorconfig/norcow.c
+++ b/embed/extmod/modtrezorconfig/norcow.c
@@ -38,17 +38,17 @@ static secbool norcow_write(uint8_t sector, uint32_t offset, uint32_t prefix, co
     ensure(flash_unlock(), NULL);
 
     // write prefix
-    ensure(flash_write_word_rel(norcow_sectors[sector], offset, prefix), NULL);
+    ensure(flash_write_word(norcow_sectors[sector], offset, prefix), NULL);
 
     if (len > 0) {
         offset += sizeof(uint32_t);
         // write data
         for (uint16_t i = 0; i < len; i++, offset++) {
-            ensure(flash_write_byte_rel(norcow_sectors[sector], offset, data[i]), NULL);
+            ensure(flash_write_byte(norcow_sectors[sector], offset, data[i]), NULL);
         }
         // pad with zeroes
         for (; offset % 4; offset++) {
-            ensure(flash_write_byte_rel(norcow_sectors[sector], offset, 0x00), NULL);
+            ensure(flash_write_byte(norcow_sectors[sector], offset, 0x00), NULL);
         }
     }
     ensure(flash_lock(), NULL);
@@ -287,7 +287,7 @@ secbool norcow_update(uint16_t key, uint16_t offset, uint32_t value)
     }
     uint32_t sector_offset = (const uint8_t*) ptr - (const uint8_t *)norcow_ptr(norcow_active_sector, 0, NORCOW_SECTOR_SIZE) + offset;
     ensure(flash_unlock(), NULL);
-    ensure(flash_write_word_rel(norcow_sectors[norcow_active_sector], sector_offset, value), NULL);
+    ensure(flash_write_word(norcow_sectors[norcow_active_sector], sector_offset, value), NULL);
     ensure(flash_lock(), NULL);
     return sectrue;
 }
diff --git a/embed/reflash/main.c b/embed/reflash/main.c
index 43f9b2b1d..f2903625c 100644
--- a/embed/reflash/main.c
+++ b/embed/reflash/main.c
@@ -26,7 +26,7 @@ static void progress_callback(int pos, int len)
     display_printf(".");
 }
 
-static void flash_from_sdcard(uint32_t target, uint32_t source, uint32_t length)
+static void flash_from_sdcard(uint8_t sector, uint32_t source, uint32_t length)
 {
     static uint32_t buf[SDCARD_BLOCK_SIZE / sizeof(uint32_t)];
 
@@ -45,7 +45,7 @@ static void flash_from_sdcard(uint32_t target, uint32_t source, uint32_t length)
             "sdcard_read_blocks");
 
         for (uint32_t j = 0; j < SDCARD_BLOCK_SIZE / sizeof(uint32_t); j++) {
-            ensure(flash_write_word(target + i * SDCARD_BLOCK_SIZE + j * sizeof(uint32_t), buf[j]), NULL);
+            ensure(flash_write_word(sector, i * SDCARD_BLOCK_SIZE + j * sizeof(uint32_t), buf[j]), NULL);
         }
     }
 }
@@ -78,13 +78,16 @@ int main(void)
 
     ensure(flash_unlock(), NULL);
 
-    sdcard_power_on();
+    ensure(sdcard_power_on(), NULL);
 
-#define BOARDLOADER_SIZE (3 * 16 * 1024)
-#define BOOTLOADER_SIZE  (128 * 1024)
+#define BOARDLOADER_CHUNK_SIZE  (16 * 1024)
+#define BOARDLOADER_TOTAL_SIZE  (3 * BOARDLOADER_CHUNK_SIZE)
+#define BOOTLOADER_TOTAL_SIZE   (128 * 1024)
 
-    flash_from_sdcard(BOARDLOADER_START, 0, BOARDLOADER_SIZE);
-    flash_from_sdcard(BOOTLOADER_START, BOARDLOADER_SIZE, BOOTLOADER_SIZE);
+    flash_from_sdcard(FLASH_SECTOR_BOARDLOADER_START,   0 * BOARDLOADER_CHUNK_SIZE, BOARDLOADER_CHUNK_SIZE);
+    flash_from_sdcard(1,                                1 * BOARDLOADER_CHUNK_SIZE, BOARDLOADER_CHUNK_SIZE);
+    flash_from_sdcard(FLASH_SECTOR_BOARDLOADER_END,     2 * BOARDLOADER_CHUNK_SIZE, BOARDLOADER_CHUNK_SIZE);
+    flash_from_sdcard(FLASH_SECTOR_BOOTLOADER,          BOARDLOADER_TOTAL_SIZE,     BOOTLOADER_TOTAL_SIZE);
 
     display_printf("done\n");
     sdcard_power_off();
diff --git a/embed/trezorhal/flash.c b/embed/trezorhal/flash.c
index 20097fa52..8ee30ae87 100644
--- a/embed/trezorhal/flash.c
+++ b/embed/trezorhal/flash.c
@@ -105,27 +105,25 @@ secbool flash_erase_sectors(const uint8_t *sectors, int len, void (*progress)(in
     return sectrue;
 }
 
-secbool flash_write_byte(uint32_t address, uint8_t data)
+secbool flash_write_byte(uint8_t sector, uint32_t offset, uint8_t data)
 {
+    uint32_t address = (uint32_t)flash_get_address(sector, offset, 1);
+    if (address == 0) {
+        return secfalse;
+    }
     return sectrue * (HAL_OK == HAL_FLASH_Program(FLASH_TYPEPROGRAM_BYTE, address, data));
 }
 
-secbool flash_write_word(uint32_t address, uint32_t data)
-{
-    return sectrue * (HAL_OK == HAL_FLASH_Program(FLASH_TYPEPROGRAM_WORD, address, data));
-}
-
-secbool flash_write_byte_rel(uint8_t sector, uint32_t offset, uint8_t data)
-{
-    return sectrue * (HAL_OK == HAL_FLASH_Program(FLASH_TYPEPROGRAM_BYTE, FLASH_SECTOR_TABLE[sector] + offset, data));
-}
-
-secbool flash_write_word_rel(uint8_t sector, uint32_t offset, uint32_t data)
+secbool flash_write_word(uint8_t sector, uint32_t offset, uint32_t data)
 {
+    uint32_t address = (uint32_t)flash_get_address(sector, offset, 4);
+    if (address == 0) {
+        return secfalse;
+    }
     if (offset % 4 != 0) {
         return secfalse;
     }
-    return sectrue * (HAL_OK == HAL_FLASH_Program(FLASH_TYPEPROGRAM_WORD, FLASH_SECTOR_TABLE[sector] + offset, data));
+    return sectrue * (HAL_OK == HAL_FLASH_Program(FLASH_TYPEPROGRAM_WORD, address, data));
 }
 
 #define FLASH_OTP_LOCK_BASE       0x1FFF7A00U
@@ -149,7 +147,8 @@ secbool flash_otp_write(uint8_t block, uint8_t offset, const uint8_t *data, uint
     ensure(flash_unlock(), NULL);
     secbool ret = secfalse;
     for (uint8_t i = 0; i < datalen; i++) {
-        ensure(flash_write_byte(FLASH_OTP_BASE + block * FLASH_OTP_BLOCK_SIZE + offset + i, data[i]), NULL);
+        uint32_t address = FLASH_OTP_BASE + block * FLASH_OTP_BLOCK_SIZE + offset + i;
+        ensure(sectrue * (HAL_OK == HAL_FLASH_Program(FLASH_TYPEPROGRAM_BYTE, address, data[i])), NULL);
     }
     ensure(flash_lock(), NULL);
     return ret;
diff --git a/embed/trezorhal/flash.h b/embed/trezorhal/flash.h
index 18274cd2a..141f3e669 100644
--- a/embed/trezorhal/flash.h
+++ b/embed/trezorhal/flash.h
@@ -52,10 +52,8 @@ const void *flash_get_address(uint8_t sector, uint32_t offset, uint32_t size);
 
 secbool __wur flash_erase_sectors(const uint8_t *sectors, int len, void (*progress)(int pos, int len));
 static inline secbool flash_erase_sector(uint8_t sector) { return flash_erase_sectors(&sector, 1, NULL); }
-secbool __wur flash_write_byte(uint32_t address, uint8_t data);
-secbool __wur flash_write_word(uint32_t address, uint32_t data);
-secbool __wur flash_write_byte_rel(uint8_t sector, uint32_t offset, uint8_t data);
-secbool __wur flash_write_word_rel(uint8_t sector, uint32_t offset, uint32_t data);
+secbool __wur flash_write_byte(uint8_t sector, uint32_t offset, uint8_t data);
+secbool __wur flash_write_word(uint8_t sector, uint32_t offset, uint32_t data);
 
 #define FLASH_OTP_NUM_BLOCKS      16
 #define FLASH_OTP_BLOCK_SIZE      32
diff --git a/embed/unix/flash.c b/embed/unix/flash.c
index 72c2d8d39..ffe967e49 100644
--- a/embed/unix/flash.c
+++ b/embed/unix/flash.c
@@ -132,7 +132,7 @@ secbool flash_erase_sectors(const uint8_t *sectors, int len, void (*progress)(in
     return sectrue;
 }
 
-secbool flash_write_byte_rel(uint8_t sector, uint32_t offset, uint8_t data)
+secbool flash_write_byte(uint8_t sector, uint32_t offset, uint8_t data)
 {
     uint8_t *flash = (uint8_t *)flash_get_address(sector, offset, sizeof(data));
     if (!flash) {
@@ -145,7 +145,7 @@ secbool flash_write_byte_rel(uint8_t sector, uint32_t offset, uint8_t data)
     return sectrue;
 }
 
-secbool flash_write_word_rel(uint8_t sector, uint32_t offset, uint32_t data)
+secbool flash_write_word(uint8_t sector, uint32_t offset, uint32_t data)
 {
     if (offset % 4) {  // we write only at 4-byte boundary
         return secfalse;