diff --git a/src/gateware/cxp_pipeline.py b/src/gateware/cxp_pipeline.py
new file mode 100644
index 0000000..f8f6277
--- /dev/null
+++ b/src/gateware/cxp_pipeline.py
@@ -0,0 +1,526 @@
+from migen import *
+from migen.genlib.cdc import MultiReg 
+from misoc.interconnect.csr import *
+from misoc.interconnect import stream
+
+from functools import reduce
+from itertools import combinations
+from operator import or_, and_
+
+char_width = 8
+char_layout = [("data", char_width), ("k", char_width//8)]
+
+word_dw = 32
+word_layout = [("data", word_dw), ("k", word_dw//8)]
+
+word_layout_dchar = [
+    ("data", word_dw),
+    ("k", word_dw//8), 
+    ("dchar", char_width), 
+    ("dchar_k", char_width//8)
+]
+
+buffer_count = 4
+buffer_depth = 512
+
+def K(x, y):
+    return ((y << 5) | x)
+
+KCode = {
+    "pak_start" : C(K(27, 7), char_width),
+    "io_ack" : C(K(28, 6), char_width), 
+    "trig_indic_28_2" : C(K(28, 2), char_width),
+    "stream_marker" : C(K(28, 3), char_width),
+    "trig_indic_28_4" : C(K(28, 4), char_width),
+    "pak_end" : C(K(29, 7), char_width),
+    "idle_comma" : C(K(28, 5), char_width),
+    "idle_alignment" : C(K(28, 1), char_width),
+}
+
+class Packet_Wrapper(Module):
+    def __init__(self):
+        self.sink = stream.Endpoint(word_layout)
+        self.source = stream.Endpoint(word_layout)
+
+        # # #
+
+        self.submodules.fsm = fsm = FSM(reset_state="IDLE")
+        
+        fsm.act("IDLE",
+            self.sink.ack.eq(1),
+            If(self.sink.stb,
+                self.sink.ack.eq(0),
+                NextState("INSERT_HEADER"),
+            )
+        )
+
+        fsm.act("INSERT_HEADER",
+            self.sink.ack.eq(0),
+            self.source.stb.eq(1),
+            self.source.data.eq(Replicate(KCode["pak_start"], 4)),
+            self.source.k.eq(Replicate(1, 4)),
+            If(self.source.ack, NextState("COPY")),
+        )
+
+        fsm.act("COPY",
+            self.sink.connect(self.source),
+            self.source.eop.eq(0),
+            If(self.sink.stb & self.sink.eop & self.source.ack,
+                NextState("INSERT_FOOTER"),
+            ),
+        )
+
+        fsm.act("INSERT_FOOTER",
+            self.sink.ack.eq(0),
+            self.source.stb.eq(1),
+            self.source.data.eq(Replicate(KCode["pak_end"], 4)),
+            self.source.k.eq(Replicate(1, 4)),
+            self.source.eop.eq(1),
+            If(self.source.ack, NextState("IDLE")),
+        )
+        
+class TX_Trigger(Module):
+    def __init__(self):
+        self.stb = Signal()
+        self.delay = Signal(char_width) 
+        self.linktrig_mode = Signal()
+
+        # # #
+
+        self.sink = stream.Endpoint(char_layout)
+        self.source = stream.Endpoint(char_layout)
+
+        # Table 15 & 16 (CXP-001-2021)
+        # Send [K28.2, K28.4, K28.4] or [K28.4, K28.2, K28.2] and 3x delay as trigger packet 
+
+        trig_packet = [Signal(char_width), Signal(char_width), Signal(char_width), self.delay, self.delay, self.delay]
+        trig_packet_k = [1, 1, 1, 0, 0, 0]
+        self.comb += [
+            If(self.linktrig_mode,
+                trig_packet[0].eq(KCode["trig_indic_28_4"]),
+                trig_packet[1].eq(KCode["trig_indic_28_2"]),
+                trig_packet[2].eq(KCode["trig_indic_28_2"]),
+            ).Else(
+                trig_packet[0].eq(KCode["trig_indic_28_2"]),
+                trig_packet[1].eq(KCode["trig_indic_28_4"]),
+                trig_packet[2].eq(KCode["trig_indic_28_4"]),
+            ),
+        ]
+        
+        self.submodules.fsm = fsm = FSM(reset_state="COPY")
+        
+        cnt = Signal(max=6)
+        fsm.act("COPY",
+            NextValue(cnt, cnt.reset),
+            self.sink.connect(self.source),
+            If(self.stb, NextState("WRITE_TRIG"))
+        )
+
+        fsm.act("WRITE_TRIG",
+            self.sink.ack.eq(0),
+            self.source.stb.eq(1),
+            self.source.data.eq(Array(trig_packet)[cnt]),
+            self.source.k.eq(Array(trig_packet_k)[cnt]),
+            If(self.source.ack,
+                If(cnt == 5,
+                    NextState("COPY"),
+                ).Else(
+                    NextValue(cnt, cnt + 1),
+                )
+            )
+        )
+
+class Idle_Word_Inserter(Module):
+    def __init__(self):
+        self.stb = Signal()
+
+        # # #
+
+        # Section 9.2.5 (CXP-001-2021)
+        # Send K28.5, K28.1, K28.1, D21.5  as idle word
+        self.submodules.fsm = fsm = FSM(reset_state="COPY")
+        
+        self.sink = stream.Endpoint(word_layout)
+        self.source = stream.Endpoint(word_layout)
+        fsm.act("COPY",
+            self.sink.connect(self.source),
+            If(self.stb, NextState("WRITE_IDLE"))
+        )
+
+        fsm.act("WRITE_IDLE",
+            self.sink.ack.eq(0),
+            self.source.stb.eq(1),
+            self.source.data.eq(Cat(KCode["idle_comma"], KCode["idle_alignment"], KCode["idle_alignment"], C(0xB5, char_width))),
+            self.source.k.eq(Cat(1, 1, 1, 0)),
+            If(self.source.ack, NextState("COPY")),
+        )
+
+
+class Trigger_ACK_Inserter(Module):
+    def __init__(self):
+        self.stb = Signal()
+
+        # # #
+
+        # Section 9.3.2 (CXP-001-2021)
+        # Send 4x K28.6 and 4x 0x01 as trigger packet ack
+        self.submodules.fsm = fsm = FSM(reset_state="COPY")
+        
+        self.sink = stream.Endpoint(word_layout)
+        self.source = stream.Endpoint(word_layout)
+        fsm.act("COPY",
+            self.sink.connect(self.source),
+            If(self.stb, NextState("WRITE_ACK0"))
+        )
+
+        fsm.act("WRITE_ACK0",
+            self.sink.ack.eq(0),
+            self.source.stb.eq(1),
+            self.source.data.eq(Replicate(KCode["io_ack"], 4)),
+            self.source.k.eq(Replicate(1, 4)),
+            If(self.source.ack, NextState("WRITE_ACK1")),
+        )
+
+        fsm.act("WRITE_ACK1",
+            self.sink.ack.eq(0),
+            self.source.stb.eq(1),
+            self.source.data.eq(Replicate(C(0x01, char_width), 4)),
+            self.source.k.eq(Replicate(0, 4)),
+            If(self.source.ack, NextState("COPY")),
+        )
+
+
+@FullMemoryWE()
+class TX_Bootstrap(Module, AutoCSR):
+    def __init__(self):
+        self.tx_word_len = CSRStorage(log2_int(buffer_depth))
+        self.tx = CSR()
+        self.tx_testseq = CSR()
+
+        self.tx_busy = CSRStatus()
+
+        # # #
+        
+        self.specials.mem = mem = Memory(word_dw, buffer_depth)
+        self.specials.mem_port = mem_port = mem.get_port()
+        self.source = stream.Endpoint(word_layout)
+
+        # increment addr in the same cycle the moment addr_inc is high
+        # as memory takes one cycle to shift to the correct addr
+        addr_next = Signal(log2_int(buffer_depth))
+        addr = Signal.like(addr_next)
+        addr_rst = Signal()
+        addr_inc = Signal()
+        self.sync += addr.eq(addr_next),
+
+        self.comb += [
+            addr_next.eq(addr),
+            If(addr_rst,
+                addr_next.eq(addr_next.reset),
+            ).Elif(addr_inc,
+                addr_next.eq(addr + 1),
+            ),
+            mem_port.adr.eq(addr_next),
+            self.source.data.eq(mem_port.dat_r)
+        ]
+
+        self.submodules.fsm = fsm = FSM(reset_state="IDLE")
+        self.sync += self.tx_busy.status.eq(~fsm.ongoing("IDLE"))
+
+        cnt = Signal(max=0xFFF)
+        fsm.act("IDLE",
+            addr_rst.eq(1),
+            If(self.tx.re, NextState("TRANSMIT")),
+            If(self.tx_testseq.re, 
+                NextValue(cnt, cnt.reset),
+                NextState("WRITE_TEST_PACKET_TYPE"),
+            )
+        )
+
+        fsm.act("TRANSMIT",
+            self.source.stb.eq(1),
+            If(self.source.ack,
+                addr_inc.eq(1),
+            ),
+            If(addr_next == self.tx_word_len.storage,
+                self.source.eop.eq(1),
+                NextState("IDLE")
+            )
+        )
+
+        fsm.act("WRITE_TEST_PACKET_TYPE",
+            self.source.stb.eq(1),
+            self.source.data.eq(Replicate(C(0x04, char_width), 4)),
+            self.source.k.eq(Replicate(0, 4)),
+            If(self.source.ack,NextState("WRITE_TEST_COUNTER"))
+        )
+
+        fsm.act("WRITE_TEST_COUNTER",
+            self.source.stb.eq(1),
+            self.source.data.eq(Cat(cnt[:8], cnt[:8]+1, cnt[:8]+2, cnt[:8]+3)),
+            self.source.k.eq(Cat(0, 0, 0, 0)),
+            If(self.source.ack,
+                If(cnt == 0xFFF-3,
+                    self.source.eop.eq(1),
+                    NextState("IDLE")
+                ).Else(
+                    NextValue(cnt, cnt + 4),
+                )
+               
+            )
+        )
+
+class RX_Debug_Buffer(Module,AutoCSR):
+    def __init__(self):
+        self.submodules.buf_out = buf_out = stream.SyncFIFO(word_layout_dchar, 128)
+        self.sink = buf_out.sink
+
+        self.inc = CSR()
+        self.dout_pak = CSRStatus(word_dw)
+        self.kout_pak = CSRStatus(word_dw//8)
+        self.dout_valid = CSRStatus()
+
+        self.sync += [
+            # output
+            buf_out.source.ack.eq(self.inc.re),
+            self.dout_pak.status.eq(buf_out.source.data),
+            self.kout_pak.status.eq(buf_out.source.k),
+            self.dout_valid.status.eq(buf_out.source.stb),
+        ]
+
+class Duplicated_Char_Decoder(Module):
+    def __init__(self):
+        self.sink = stream.Endpoint(word_layout)
+        self.source = stream.Endpoint(word_layout_dchar)
+
+        # # #
+
+
+        # For duplicated characters, an error correction method (e.g. majority voting) is required to meet the CXP spec:
+        # RX decoder should immune to single bit errors when handling duplicated characters - Section 9.2.2.1 (CXP-001-2021)
+        # 
+        #
+        #                                 32
+        #             +--->  buffer  -----/-----+
+        #         32  |                         |            32+8(dchar)
+        # sink ---/---+                         ---> source -----/-----> downstream
+        #             |                8(dchar) |                        decoders
+        #             +---> majority -----/-----+
+        #                   voting
+        # 
+        #
+        # Due to the tight setup/hold time requiremnt for 12.5Gbps CXP, the voting logic cannot be implemented as combinational logic
+        # Hence, a pipeline approach is needed to avoid any s/h violation, where the majority voting result are pre-calculate and injected into the bus immediate after the PHY.
+        # And any downstream modules can access the voting result without implementing the voting logic inside the decoder
+
+        # cycle 1 - buffer data & calculate intermediate result  
+        buffer = stream.Endpoint(word_layout)
+        self.sync += [
+            If((~buffer.stb | buffer.ack),
+                buffer.stb.eq(self.sink.stb),
+                buffer.payload.eq(self.sink.payload),
+            )
+        ]
+        self.comb += self.sink.ack.eq(~buffer.stb | buffer.ack)
+        
+        # calculate ABC, ABD, ACD, BCD  
+        char = [[self.sink.data[i*8:(i+1)*8], self.sink.k[i]] for i in range(4)]
+        voters = [Record([("data", 8), ("k", 1)]) for _ in range(4)]
+
+        for i, comb in enumerate(combinations(char, 3)):
+            self.sync += [
+                If((~buffer.stb | buffer.ack),
+                    voters[i].data.eq(reduce(and_, [code[0] for code in comb])),
+                    voters[i].k.eq(reduce(and_, [code[1] for code in comb])),
+                )
+            ]
+
+
+        # cycle 2 - inject the voting result 
+        self.sync += [
+            If((~self.source.stb | self.source.ack),
+                self.source.stb.eq(buffer.stb),
+                self.source.data.eq(buffer.data),
+                self.source.k.eq(buffer.k),
+                self.source.dchar.eq(Replicate(reduce(or_, [v.data for v in voters]), 4)),
+                self.source.dchar_k.eq(Replicate(reduce(or_, [v.k for v in voters]), 4)),
+            )
+        ]
+        self.comb += buffer.ack.eq(~self.source.stb | self.source.ack)
+
+
+@FullMemoryWE()
+class RX_Bootstrap(Module):
+    def __init__(self):
+        self.packet_type = Signal(8)
+
+        self.decode_err = Signal()
+        self.test_err = Signal()
+        self.buffer_err = Signal()
+        # # #
+
+        # TODO: heartbeat
+        type = {
+            "data_stream": 0x01,
+            "control_ack_no_tag": 0x03,
+            "test_packet": 0x04,
+            "control_ack_with_tag": 0x06,
+            "event": 0x07,
+            "heartbeat": 0x09,
+        }
+
+        self.sink = stream.Endpoint(word_layout_dchar)
+        self.source = stream.Endpoint(word_layout_dchar)
+
+        self.submodules.fsm = fsm = FSM(reset_state="IDLE")
+
+        fsm.act("IDLE",
+            self.sink.ack.eq(1),
+            If((self.sink.stb & (self.sink.dchar == KCode["pak_start"]) & (self.sink.dchar_k == 1)),
+                NextState("DECODE"),
+            )
+        )
+
+        cnt = Signal(max=0x100)
+        addr_nbits = log2_int(buffer_depth)
+        addr = Signal(addr_nbits)
+        fsm.act("DECODE",
+            self.sink.ack.eq(1),
+            If(self.sink.stb,
+                NextValue(self.packet_type, self.sink.dchar),
+
+                Case(self.sink.dchar, {
+                    type["data_stream"]: NextState("STREAMING"),
+                    type["test_packet"]: [
+                        NextValue(cnt, cnt.reset),
+                        NextState("VERIFY_TEST_PATTERN"),
+                    ],
+                    type["control_ack_no_tag"]:[
+                        NextValue(addr, addr.reset),
+                        NextState("LOAD_BUFFER"),
+                    ],
+                    type["control_ack_with_tag"]:[
+                        NextValue(addr, addr.reset),
+                        NextState("LOAD_BUFFER"),
+                    ],
+                    type["event"]: [
+                        NextValue(addr, addr.reset),
+                        NextState("LOAD_BUFFER"),
+                    ],
+                    "default": [
+                         self.decode_err.eq(1),
+                         # wait till next valid packet
+                         NextState("IDLE"),
+                    ],
+                }),
+            )
+        )
+        # For stream data packet
+        fsm.act("STREAMING",
+            If((self.sink.stb & (self.sink.dchar == KCode["pak_end"]) & (self.sink.dchar_k == 1)),
+                # discard K29,7
+                self.sink.ack.eq(1),
+                NextState("IDLE")
+            ).Else(
+                self.sink.connect(self.source),
+            )      
+        )
+
+        # Section 9.9.1 (CXP-001-2021)
+        # the received test data packet (0x00, 0x01 ... 0xFF) 
+        # need to be compared against the local test sequence generator
+        fsm.act("VERIFY_TEST_PATTERN",
+            self.sink.ack.eq(1),
+            If(self.sink.stb,
+                If(((self.sink.dchar == KCode["pak_end"]) & (self.sink.dchar_k == 1)),
+                    NextState("IDLE"),
+                ).Else(
+                    If(((self.sink.data != Cat(cnt, cnt+1, cnt+2, cnt+3))),  
+                        self.test_err.eq(1),
+                    ),
+                    If(cnt == 0xFC,
+                        NextValue(cnt, cnt.reset),
+                    ).Else(
+                        NextValue(cnt, cnt + 4)
+                    )
+                )
+            )
+                
+        )
+
+        # A circular buffer for firmware to read packet from
+        self.specials.mem = mem = Memory(word_dw, buffer_count*buffer_depth)
+        self.specials.mem_port = mem_port = mem.get_port(write_capable=True)
+
+        write_ptr = Signal(log2_int(buffer_count))
+        self.write_ptr_sys = Signal.like(write_ptr)
+        self.specials += MultiReg(write_ptr, self.write_ptr_sys),
+
+        self.comb += [
+            mem_port.adr[:addr_nbits].eq(addr),
+            mem_port.adr[addr_nbits:].eq(write_ptr),
+        ]
+
+        # For control ack, event packet
+        fsm.act("LOAD_BUFFER",
+            mem_port.we.eq(0),
+            self.sink.ack.eq(1),
+            If(self.sink.stb,
+                If(((self.sink.dchar == KCode["pak_end"]) & (self.sink.dchar_k == 1)),
+                    NextState("MOVE_BUFFER_PTR"),
+                ).Else(
+                    mem_port.we.eq(1),
+                    mem_port.dat_w.eq(self.sink.data),
+                    NextValue(addr, addr + 1),
+                    If(addr == buffer_depth - 1,
+                        # discard the packet
+                        self.buffer_err.eq(1),
+                        NextState("IDLE"),
+                    )
+                )
+            )
+        )
+
+        self.read_ptr_rx = Signal.like(write_ptr)
+        fsm.act("MOVE_BUFFER_PTR",
+            self.sink.ack.eq(0),
+            If(write_ptr + 1 == self.read_ptr_rx,
+                # if next one hasn't been read, overwrite the current buffer when new packet comes in
+                self.buffer_err.eq(1),
+            ).Else(
+                NextValue(write_ptr, write_ptr + 1),
+            ),
+            NextState("IDLE"),
+        )
+
+class Trigger_Ack_Checker(Module, AutoCSR):
+    def __init__(self):
+        self.sink = stream.Endpoint(word_layout_dchar)
+        self.source = stream.Endpoint(word_layout_dchar)
+
+        self.ack = Signal()
+
+        # # #
+
+        self.submodules.fsm = fsm = FSM(reset_state="COPY")
+
+        fsm.act("COPY",
+            If((self.sink.stb & (self.sink.dchar == KCode["io_ack"]) & (self.sink.dchar_k == 1)),
+                # discard K28,6
+                self.sink.ack.eq(1),
+                NextState("CHECK_ACK")
+            ).Else(
+                self.sink.connect(self.source),
+            )
+        )
+
+        fsm.act("CHECK_ACK",
+            If(self.sink.stb,
+                NextState("COPY"),
+                # discard the word after K28,6
+                self.sink.ack.eq(1),
+                If((self.sink.dchar == 0x01) & (self.sink.dchar_k == 0),
+                    self.ack.eq(1),
+                )
+            )
+        )