diff --git a/pm3py/core/hf_iso14a.py b/pm3py/core/hf_iso14a.py
index ad129fc..58ec4a4 100644
--- a/pm3py/core/hf_iso14a.py
+++ b/pm3py/core/hf_iso14a.py
@@ -71,26 +71,58 @@ class HF14ACommands:
 
     async def sniff(self, param: int = 0) -> dict:
         """Sniff ISO14443A traffic."""
-        resp = await self._t.send_mix(
-            Cmd.HF_ISO14443A_SNIFF, arg0=param, timeout=30.0,
+        resp = await self._t.send_ng(
+            Cmd.HF_ISO14443A_SNIFF, payload=bytes([param]), timeout=30.0,
         )
         return {"status": resp.status}
 
-    async def sim(self, uid: bytes, sak: int = 0x08, atqa: bytes = b"\x04\x00",
-                  flags: int = 0) -> dict:
-        """Simulate ISO14443A card."""
-        if len(uid) == 4:
-            uid_flag = 0x0010
-        elif len(uid) == 7:
-            uid_flag = 0x0020
-        elif len(uid) == 10:
-            uid_flag = 0x0030
+    async def sim(self, tagtype: int = 1, uid: bytes = b"", exit_after: int = 0,
+                  flags: int = 0, rats: bytes = b"",
+                  ulauth_1a1: bytes = b"", ulauth_1a2: bytes = b"",
+                  ulauth_1a2_mirror: bool = False) -> dict:
+        """Simulate an ISO14443A tag.
+
+        tagtype selects the emulated tag: 1=MIFARE Classic 1k, 2=Ultralight,
+        3=DESFire, 4=ISO14443-4, 5=Tnp3xxx, 6=MF Mini, 7=MFU EV1/NTAG215,
+        8=MFC 4k, 9=FM11RF005SH, 10=ST25TA, 11=JCOP, 12=Seos, 13=ULC,
+        14=ULAES, 15=MF Plus.
+
+        uid: 4, 7, or 10 raw bytes. Empty = take UID from emulator memory.
+        exit_after: stop after N reader reads (0 = infinite).
+        ulauth_1a1/ulauth_1a2: ULC (8 byte) / ULAES (16 byte) auth replies.
+        """
+        # Fold the UID length into flags per FLAG_SET_UID_IN_DATA (pm3_cmd.h).
+        if uid:
+            if len(uid) == 4:
+                uid_flag = 0x0010  # FLAG_4B_UID_IN_DATA
+            elif len(uid) == 7:
+                uid_flag = 0x0020  # FLAG_7B_UID_IN_DATA
+            elif len(uid) == 10:
+                uid_flag = 0x0030  # FLAG_10B_UID_IN_DATA
+            else:
+                raise ValueError("UID must be 4, 7, or 10 bytes")
         else:
-            raise ValueError("UID must be 4, 7, or 10 bytes")
+            uid_flag = 0x0000  # FLAG_UID_IN_EMUL
 
-        flag_val = flags | uid_flag | 0x0001  # FLAG_INTERACTIVE
-        payload = atqa + bytes([sak]) + uid
-        resp = await self._t.send_mix(
-            Cmd.HF_ISO14443A_SIMULATE, arg0=flag_val, timeout=60.0, payload=payload,
+        flag_val = (flags & ~0x0030) | uid_flag  # FLAG_MASK_UID = 0x0030
+
+        # struct { u8 tagtype; u16 flags; u8 uid[10]; u8 exitAfter;
+        #          u8 rats[20]; u8 ulauth_1a1_len; u8 ulauth_1a2_len;
+        #          u8 ulauth_1a1[16]; u8 ulauth_1a2[16]; bool mirror; } PACKED
+        payload = struct.pack(
+            "<BH10sB20sBB16s16sB",
+            tagtype & 0xFF,
+            flag_val & 0xFFFF,
+            uid.ljust(10, b"\x00")[:10],
+            exit_after & 0xFF,
+            rats.ljust(20, b"\x00")[:20],
+            len(ulauth_1a1),
+            len(ulauth_1a2),
+            ulauth_1a1.ljust(16, b"\x00")[:16],
+            ulauth_1a2.ljust(16, b"\x00")[:16],
+            1 if ulauth_1a2_mirror else 0,
+        )
+        resp = await self._t.send_ng(
+            Cmd.HF_ISO14443A_SIMULATE, payload=payload, timeout=60.0,
         )
         return {"status": resp.status}
diff --git a/tests/test_hf_14a.py b/tests/test_hf_14a.py
index 5e1bfec..636f26a 100644
--- a/tests/test_hf_14a.py
+++ b/tests/test_hf_14a.py
@@ -23,3 +23,46 @@ def test_14a_scan():
     assert result["uid"] == "04010203040506"
     assert result["uid_len"] == 7
     assert result["sak"] == 0x08
+
+
+def test_14a_sim_packs_ng_struct():
+    t = AsyncMock()
+    hf14a = HF14ACommands(t)
+    t.send_ng.return_value = PM3Response(cmd=Cmd.HF_ISO14443A_SIMULATE, status=0,
+                                         reason=0, ng=True, data=b"", oldarg=[])
+    uid = b"\x04\x01\x02\x03"
+    result = asyncio.get_event_loop().run_until_complete(
+        hf14a.sim(tagtype=7, uid=uid, exit_after=3))
+    assert result["status"] == 0
+    args, kwargs = t.send_ng.call_args
+    assert args[0] == Cmd.HF_ISO14443A_SIMULATE
+    payload = kwargs["payload"]
+    assert len(payload) == 69  # PACKED firmware struct size
+    tagtype, flags = struct.unpack_from("<BH", payload, 0)
+    assert tagtype == 7
+    assert flags & 0x0030 == 0x0010  # FLAG_4B_UID_IN_DATA
+    assert payload[3:7] == uid      # uid[10] field, first 4 bytes
+    assert payload[13] == 3         # exitAfter
+
+
+def test_14a_sim_no_uid_uses_emul_flag():
+    t = AsyncMock()
+    hf14a = HF14ACommands(t)
+    t.send_ng.return_value = PM3Response(cmd=Cmd.HF_ISO14443A_SIMULATE, status=0,
+                                         reason=0, ng=True, data=b"", oldarg=[])
+    asyncio.get_event_loop().run_until_complete(hf14a.sim(tagtype=1))
+    payload = t.send_ng.call_args.kwargs["payload"]
+    _, flags = struct.unpack_from("<BH", payload, 0)
+    assert flags & 0x0030 == 0x0000  # FLAG_UID_IN_EMUL
+
+
+def test_14a_sniff_sends_ng_param_byte():
+    t = AsyncMock()
+    hf14a = HF14ACommands(t)
+    t.send_ng.return_value = PM3Response(cmd=Cmd.HF_ISO14443A_SNIFF, status=0,
+                                         reason=0, ng=True, data=b"", oldarg=[])
+    result = asyncio.get_event_loop().run_until_complete(hf14a.sniff(2))
+    assert result["status"] == 0
+    args, kwargs = t.send_ng.call_args
+    assert args[0] == Cmd.HF_ISO14443A_SNIFF
+    assert kwargs["payload"] == bytes([2])