diff --git a/BLE/DLD154Pro_Peripheral_28K/APP/include/rs485_modbus.h b/BLE/DLD154Pro_Peripheral_28K/APP/include/rs485_modbus.h
index b726477..5848e9f 100644
--- a/BLE/DLD154Pro_Peripheral_28K/APP/include/rs485_modbus.h
+++ b/BLE/DLD154Pro_Peripheral_28K/APP/include/rs485_modbus.h
@@ -36,6 +36,11 @@
  * addr(1) + fc(1) + byte_cnt(1) + data(38) + crc(2) = 43 */
 #define MB_FULL_DATA_FRAME_LEN   43
 
+/* FC 0x03/0x04 读寄存器缓冲 (Modbus 标准: max qty = 0x007D = 125) */
+#define MB_MAX_READ_REGS          125      /* 单次读取最大寄存器数 */
+#define MB_MAX_DATA_BYTES         250      /* 125 × 2 字节 */
+#define MB_RESP_BUF_SIZE          (5 + MB_MAX_DATA_BYTES)  /* addr+fc+bc+data+crc */
+
 /*===========================================================================
  * API
  *===========================================================================*/
diff --git a/BLE/DLD154Pro_Peripheral_28K/APP/rs485_modbus.c b/BLE/DLD154Pro_Peripheral_28K/APP/rs485_modbus.c
index 0d4ec5a..aa9a222 100644
--- a/BLE/DLD154Pro_Peripheral_28K/APP/rs485_modbus.c
+++ b/BLE/DLD154Pro_Peripheral_28K/APP/rs485_modbus.c
@@ -463,12 +463,12 @@ static void handle_read_input_regs(const uint8_t *rx, uint8_t rx_len)
     uint16_t start_addr = ((uint16_t)rx[2] << 8) | rx[3];
     uint16_t quantity   = ((uint16_t)rx[4] << 8) | rx[5];
 
-    if (quantity == 0 || quantity > 125) {
+    if (quantity == 0 || quantity > MB_MAX_READ_REGS) {
         send_exception(0x04, 0x03);
         return;
     }
 
-    uint8_t  data_buf[250];
+    uint8_t  data_buf[MB_MAX_DATA_BYTES];
     uint16_t reg_addr;
 
     for (uint16_t i = 0; i < quantity; i++) {
@@ -483,7 +483,7 @@ static void handle_read_input_regs(const uint8_t *rx, uint8_t rx_len)
     }
 
     uint8_t  byte_cnt = (uint8_t)(quantity * 2);
-    uint8_t  buf[5 + 250];  /* addr + fc + bc + data + crc */
+    uint8_t  buf[MB_RESP_BUF_SIZE];
     uint16_t crc;
 
     buf[0] = g_rs485_id & 0xFF;
@@ -543,12 +543,12 @@ static void handle_read_holding_regs(const uint8_t *rx, uint8_t rx_len)
     uint16_t start_addr = ((uint16_t)rx[2] << 8) | rx[3];
     uint16_t quantity   = ((uint16_t)rx[4] << 8) | rx[5];
 
-    if (quantity == 0 || quantity > 125) {
+    if (quantity == 0 || quantity > MB_MAX_READ_REGS) {
         send_exception(0x03, 0x03);
         return;
     }
 
-    uint8_t  data_buf[250];
+    uint8_t  data_buf[MB_MAX_DATA_BYTES];
 
     for (uint16_t i = 0; i < quantity; i++) {
         uint16_t reg_addr = start_addr + i;
@@ -562,7 +562,7 @@ static void handle_read_holding_regs(const uint8_t *rx, uint8_t rx_len)
     }
 
     uint8_t  byte_cnt = (uint8_t)(quantity * 2);
-    uint8_t  buf[5 + 250];
+    uint8_t  buf[MB_RESP_BUF_SIZE];
     uint16_t crc;
 
     buf[0] = g_rs485_id & 0xFF;