diff --git a/doc/libmodbus.txt b/doc/libmodbus.txt
index f8597d0..6bcdf06 100644
--- a/doc/libmodbus.txt
+++ b/doc/libmodbus.txt
@@ -143,12 +143,18 @@ Macros for data manipulation::
 
 - MODBUS_GET_HIGH_BYTE(data), extracts the high byte from a byte
 - MODBUS_GET_LOW_BYTE(data), extracts the low byte from a byte
+- MODBUS_GET_INT64_FROM_INT16(tab_int16, index), builds an int64 from the four
+  first int16 starting at tab_int16[index]
 - MODBUS_GET_INT32_FROM_INT16(tab_int16, index), builds an int32 from the two
   first int16 starting at tab_int16[index]
 - MODBUS_GET_INT16_FROM_INT8(tab_int8, index), builds an int16 from the two
   first int8 starting at tab_int8[index]
 - MODBUS_SET_INT16_TO_INT8(tab_int8, index, value), set an int16 value into
   the two first bytes starting at tab_int8[index]
+- MODBUS_SET_INT32_TO_INT16(tab_int16, index, value), set an int32 value into
+  the two first int16 starting at tab_int16[index]
+- MODBUS_SET_INT64_TO_INT16(tab_int16, index, value), set an int64 value into
+  the four first int16 starting at tab_int16[index]
 
 Handling of bits and bytes::
     linkmb:modbus_set_bits_from_byte[3]
diff --git a/src/modbus.h b/src/modbus.h
index 4381aad..1207de3 100644
--- a/src/modbus.h
+++ b/src/modbus.h
@@ -230,6 +230,11 @@ MODBUS_API int modbus_reply_exception(modbus_t *ctx, const uint8_t *req,
 
 #define MODBUS_GET_HIGH_BYTE(data) (((data) >> 8) & 0xFF)
 #define MODBUS_GET_LOW_BYTE(data) ((data) & 0xFF)
+#define MODBUS_GET_INT64_FROM_INT16(tab_int16, index) \
+    (((int64_t)tab_int16[(index)    ] << 48) + \
+     ((int64_t)tab_int16[(index) + 1] << 32) + \
+     ((int64_t)tab_int16[(index) + 2] << 16) + \
+      (int64_t)tab_int16[(index) + 3])
 #define MODBUS_GET_INT32_FROM_INT16(tab_int16, index) ((tab_int16[(index)] << 16) + tab_int16[(index) + 1])
 #define MODBUS_GET_INT16_FROM_INT8(tab_int8, index) ((tab_int8[(index)] << 8) + tab_int8[(index) + 1])
 #define MODBUS_SET_INT16_TO_INT8(tab_int8, index, value) \
@@ -237,6 +242,18 @@ MODBUS_API int modbus_reply_exception(modbus_t *ctx, const uint8_t *req,
         tab_int8[(index)] = (value) >> 8;  \
         tab_int8[(index) + 1] = (value) & 0xFF; \
     } while (0)
+#define MODBUS_SET_INT32_TO_INT16(tab_int16, index, value) \
+    do { \
+        tab_int16[(index)    ] = (value) >> 16; \
+        tab_int16[(index) + 1] = (value); \
+    } while (0)
+#define MODBUS_SET_INT64_TO_INT16(tab_int16, index, value) \
+    do { \
+        tab_int16[(index)    ] = (value) >> 48; \
+        tab_int16[(index) + 1] = (value) >> 32; \
+        tab_int16[(index) + 2] = (value) >> 16; \
+        tab_int16[(index) + 3] = (value); \
+    } while (0)
 
 MODBUS_API void modbus_set_bits_from_byte(uint8_t *dest, int idx, const uint8_t value);
 MODBUS_API void modbus_set_bits_from_bytes(uint8_t *dest, int idx, unsigned int nb_bits,