From 64809fcb31c13290ee66d12e0bf76d14eb6d0953 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?St=C3=A9phanie=20Amati?= <stephanie.amati@gmail.com>
Date: Thu, 8 Oct 2026 23:30:54 +0100
Subject: [PATCH] Corrected F4 sector number calculation for F413 and F423.

---
 src/stlink-lib/calculate.c     | 23 +++++++++++++++++++----
 src/stlink-lib/calculate.h     |  2 +-
 src/stlink-lib/common_flash.c  | 10 ++--------
 src/stlink-lib/common_legacy.c |  9 ++++++---
 4 files changed, 28 insertions(+), 16 deletions(-)

diff --git a/src/stlink-lib/calculate.c b/src/stlink-lib/calculate.c
index b90c7a7b..ea446d48 100644
--- a/src/stlink-lib/calculate.c
+++ b/src/stlink-lib/calculate.c
@@ -17,13 +17,28 @@
 #include "read_write.h"
 
 
-uint32_t calculate_F4_sectornum(uint32_t flashaddr) {
+uint32_t calculate_F4_sectornum(stlink_t *sl, uint32_t flashaddr) {
   uint32_t offset = 0;
   flashaddr &= ~STM32_FLASH_BASE; // page now holding the actual flash address
 
-  if(flashaddr >= 0x100000) {
-    offset = 12;
-    flashaddr -= 0x100000;
+  /* The F413 and F423 chips have a single bank flash */
+  if (sl->chip_id != STM32_CHIPID_F413) {
+    /* Dual bank flash of 1MB have a discontinuity in their sector 
+       numbering. Sector 7 is the last from the first bank and sector 12 is
+       the first from the second bank. */
+    if (sl->flash_size <= 1024*1024) {
+      if (flashaddr >= 0x080000) {
+        offset = 12;
+        flashaddr -= 0x080000;
+      } 
+    }
+    /* Dual bank flash of 2MB */
+    else {
+      if (flashaddr >= 0x100000) {
+        offset = 12;
+        flashaddr -= 0x100000;
+      }
+    }
   }
 
   if(flashaddr < 0x4000) {
diff --git a/src/stlink-lib/calculate.h b/src/stlink-lib/calculate.h
index 726f027a..527d8f06 100644
--- a/src/stlink-lib/calculate.h
+++ b/src/stlink-lib/calculate.h
@@ -19,7 +19,7 @@
 #include <stlink.h>
 
 
-uint32_t calculate_F4_sectornum(uint32_t);
+uint32_t calculate_F4_sectornum(stlink_t *, uint32_t);
 uint32_t calculate_F7_sectornum(uint32_t);
 uint32_t calculate_H7_sectornum(stlink_t *, uint32_t, uint32_t);
 uint32_t calculate_L4_page(stlink_t *, uint32_t);
diff --git a/src/stlink-lib/common_flash.c b/src/stlink-lib/common_flash.c
index 570ab78c..36e16942 100644
--- a/src/stlink-lib/common_flash.c
+++ b/src/stlink-lib/common_flash.c
@@ -1234,17 +1234,11 @@ int32_t stlink_erase_flash_page(stlink_t *sl, stm32_addr_t flashaddr) {
     // STM32F4
     } else {
       // calculate the actual page from the address
-      uint32_t sector = calculate_F4_sectornum(flashaddr);
+      uint32_t sector = calculate_F4_sectornum(sl, flashaddr);
 
       fprintf(stderr, "EraseFlash - Sector:0x%x Size:0x%x ", sector,
               stlink_calculate_pagesize(sl, flashaddr));
 
-      // the SNB values for flash sectors in the second bank do not directly
-      // follow the values for the first bank on 2mb devices...
-      if(sector >= 12) {
-        sector += 4;
-      }
-
       write_flash_cr_snb(sl, sector, BANK_1);
     }
 
@@ -1567,7 +1561,7 @@ int32_t stlink_erase_flash_section(stlink_t *sl, stm32_addr_t base_addr, uint32_
       return (-1);
     }
 
-    fprintf(stdout, "-> Flash page at %#x erased (size: %#x)\n", addr, page_size);
+    fprintf(stdout, "-> Flash sector at %#x erased (size: %#x)\n", addr, page_size);
     fflush(stdout);
 
     // check the next page is within the range to erase
diff --git a/src/stlink-lib/common_legacy.c b/src/stlink-lib/common_legacy.c
index ea92851d..08985560 100644
--- a/src/stlink-lib/common_legacy.c
+++ b/src/stlink-lib/common_legacy.c
@@ -1047,10 +1047,13 @@ uint32_t stlink_calculate_pagesize(stlink_t *sl, uint32_t flashaddr) {
       (sl->chip_id == STM32_CHIPID_F412) ||
       (sl->chip_id == STM32_CHIPID_F410) ||
       (sl->chip_id == STM32_CHIPID_F413)) {
-    uint32_t sector = calculate_F4_sectornum(flashaddr);
+    uint32_t sector = calculate_F4_sectornum(sl, flashaddr);
 
-    if(sector >= 12) {
-      sector -= 12;
+    /* Correct sector for dual bank flash memories only */
+    if (sl->chip_id != STM32_CHIPID_F413) {
+      if(sector >= 12) {
+        sector -= 12;
+      }
     }
 
     if(sector < 4) {