diff --git a/hal/renesas-rx.c b/hal/renesas-rx.c
index 0cb3fe70f..a31b250bc 100644
--- a/hal/renesas-rx.c
+++ b/hal/renesas-rx.c
@@ -466,9 +466,12 @@ int RAMFUNCTION hal_flash_write(uint32_t addr, const uint8_t *data, int len)
         FLASH_FACI_CMD8 = FLASH_FACI_CMD_PROGRAM;
         FLASH_FACI_CMD8 = FLASH_FACI_CMD_PROGRAM_CODE_LENGTH;
 
-        /* write 128 * 2 bytes */
+        /* write 64 * 2 bytes */
         for (i=0; i < FLASH_FACI_CMD_PROGRAM_CODE_LENGTH; i++) {
             FLASH_FACI_CMD16 = *data16++;
+
+            /* wait for data buffer not full */
+            while (FLASH_FSTATR & FLASH_FSTATR_DBFULL);
         }
 
         FLASH_FACI_CMD8 = FLASH_FACI_CMD_FINAL;
@@ -476,7 +479,10 @@ int RAMFUNCTION hal_flash_write(uint32_t addr, const uint8_t *data, int len)
         /* Wait for FCU operation to complete */
         while ((FLASH_FSTATR & FLASH_FSTATR_FRDY) == 0);
 
-        len += (FLASH_FACI_CMD_PROGRAM_CODE_LENGTH * 2);
+        len -= (FLASH_FACI_CMD_PROGRAM_CODE_LENGTH *
+                FLASH_FACI_CMD_PROGRAM_DATA_LENGTH);
+        addr += (FLASH_FACI_CMD_PROGRAM_CODE_LENGTH *
+                FLASH_FACI_CMD_PROGRAM_DATA_LENGTH);
     }
     return 0;
 }
@@ -599,14 +605,18 @@ static int test_flash(void)
 
 #ifndef TEST_FLASH_READONLY
     /* Erase sector */
+    hal_flash_unlock();
     ret = hal_flash_erase(TEST_ADDRESS, sizeof(pageData));
+    hal_flash_lock();
     wolfBoot_printf("Erase Sector: Ret %d\n", ret);
 
     /* Write Pages */
     for (i=0; i<sizeof(pageData); i++) {
         ((uint8_t*)pageData)[i] = (i & 0xff);
     }
+    hal_flash_unlock();
     ret = hal_flash_write(TEST_ADDRESS, (uint8_t*)pageData, sizeof(pageData));
+    hal_flash_lock();
     wolfBoot_printf("Write Page: Ret %d\n", ret);
 #endif /* !TEST_FLASH_READONLY */
 
diff --git a/hal/renesas-rx.h b/hal/renesas-rx.h
index 3c33a278f..3744d948b 100644
--- a/hal/renesas-rx.h
+++ b/hal/renesas-rx.h
@@ -178,6 +178,7 @@ void hal_delay_us(uint32_t us);
 #define FLASH_FAEINT_CFAEIE  (1 << 7)
 
 #define FLASH_FSADDR (*(volatile uint32_t *)(0x007FE030))
+#define FLASH_FEADDR (*(volatile uint32_t *)(0x007FE034))
 
 #define FLASH_FAWMON (*(volatile uint32_t *)(0x007FE0DC))
 #define FLASH_FAWMON_FAWS(a)  ((a) & 0xFFF)        /* Flash Access Window Start Address * 2 */
@@ -221,7 +222,7 @@ void hal_delay_us(uint32_t us);
 
 /* FCAI Commands (RX72N RM Table 62.11) */
 #define FLASH_FACI_CMD_PROGRAM                  0xE8
-#define FLASH_FACI_CMD_PROGRAM_CODE_LENGTH      128
+#define FLASH_FACI_CMD_PROGRAM_CODE_LENGTH      64
 #define FLASH_FACI_CMD_PROGRAM_DATA_LENGTH      2
 #define FLASH_FACI_CMD_BLOCK_ERASE              0x20
 #define FLASH_FACI_CMD_PROGRAM_ERASE_SUSPEND    0xB0