diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..328167a
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+/work/
+*.o
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..1de204d
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,125 @@
+.SECONDARY:
+
+SYNTH_TOOLCHAIN ?= symbiflow
+
+WORKDIR            = $(PWD)/work
+GHDL_WORKDIR       = $(WORKDIR)/ghdl
+SYMBIYOSYS_WORKDIR = $(WORKDIR)/symbiyosys
+LITEX_WORKDIR      = $(WORKDIR)/litex
+SYNTH_WORKDIR      = $(WORKDIR)/synth/$(SYNTH_TOOLCHAIN)
+
+SIM_DIR   = sim
+VHDL_DIR  = vhdl
+
+WORKLIB_NAME = splink
+
+VHDL_FILES = $(wildcard $(VHDL_DIR)/*.vhdl)
+VERILOG_FILES = $(LITEX_WORKDIR)/gateware/liteeth_core.v
+SBY_FILES =
+
+SIM_ENTITY        = splink_tb
+SYNTH_ENTITY      = arty_a7
+YOSYS_MODULE_NAME = arty_a7
+
+GHDL = ghdl
+VHDL_STD = 08
+GHDL_FLAGS    = --std=$(VHDL_STD) --work=$(WORKLIB_NAME) --workdir=$(GHDL_WORKDIR) -g
+SIM_RUN_FLAGS = --max-stack-alloc=0 --assert-level=warning --ieee-asserts=disable-at-0
+
+GTKWAVE = gtkwave
+
+# synthesis
+
+XDC = $(PWD)/arty_a7_35.xdc
+
+PART = xc7a35tcsg324-1
+
+YOSYS = yosys
+
+XRAY_DATABASE = /usr/share/xray/database/artix7
+
+NEXTPNR = nextpnr-xilinx
+BBASM   = bbasm
+FASM2FRAMES = fasm2frames
+FRAMES2BIT  = xc7frames2bit
+OPENFPGALOADER = openFPGALoader
+
+GHDL_YOSYS_PLUGIN = ghdl
+
+SBY = sby -fd '$(SYMBIYOSYS_WORKDIR)' --yosys='$(YOSYS) -m $(GHDL_YOSYS_PLUGIN)'
+
+# ====================
+# END OF CONFIGURATION
+# ====================
+
+SIM_WAVE = $(SIM_DIR)/$(SIM_ENTITY).ghw
+# for only capturing select signals
+SIM_WAVEOPTS = $(SIM_DIR)/$(SIM_ENTITY).waveopt
+SIM_WAVE_SAVE = $(SIM_DIR)/$(SIM_ENTITY).gtkw
+
+ifneq (,$(wildcard $(SIM_WAVEOPTS)))
+SIM_RUN_FLAGS += --read-wave-opt=$(SIM_WAVEOPTS)
+endif
+
+ifeq ($(SYNTH_TOOLCHAIN),symbiflow)
+include Makefile.symbiflow
+else ifeq ($(SYNTH_TOOLCHAIN),nextpnr)
+include Makefile.nextpnr
+else
+$(error Bad PNR toolchain: expected one of symbiflow, nextpnr)
+endif
+
+# =======
+# PHONIES
+# =======
+
+.PHONY: all simonly wave
+
+# default target
+all: bitstream
+
+$(GHDL_WORKDIR)/work-obj$(VHDL_STD).cf: | $(GHDL_WORKDIR)
+	$(GHDL) import $(GHDL_FLAGS) $(VHDL_FILES)
+
+$(LITEX_WORKDIR)/gateware/liteeth_core.v: gen_liteeth.py
+	./gen_liteeth.py --output-dir $(LITEX_WORKDIR)
+
+simonly: $(VHDL_FILES) | $(GHDL_WORKDIR)/work-obj$(VHDL_STD).cf
+	$(GHDL) make $(GHDL_FLAGS) $(SIM_ENTITY)
+	$(GHDL) run $(GHDL_FLAGS) $(SIM_ENTITY) $(SIM_RUN_FLAGS)
+
+wave: $(VHDL_FILES)
+	$(GHDL) make $(GHDL_FLAGS) $(SIM_ENTITY)
+	$(GHDL) run $(GHDL_FLAGS) $(SIM_ENTITY) $(SIM_RUN_FLAGS) --wave=$(SIM_WAVE)
+	$(GTKWAVE) $(SIM_WAVE) $(SIM_WAVE_SAVE)
+
+.PHONY: check check-formal
+check: check-formal
+
+check-formal:
+	$(foreach f,$(SBY_FILES),$(SBY) $(f))
+
+.PHONY: synth show bitstream flash
+synth: $(SYNTH_OUTPUT_FILE)
+
+show: $(SYNTH_OUTPUT_FILE)
+	$(YOSYS) -p show $<
+
+bitstream: $(SYNTH_WORKDIR)/$(YOSYS_MODULE_NAME).bit
+
+flash: $(SYNTH_WORKDIR)/$(YOSYS_MODULE_NAME).bit
+	$(OPENFPGALOADER) -b arty $<
+
+.PHONY: clean
+clean:
+	rm -rf $(WORKDIR)
+
+$(GHDL_WORKDIR) $(SYNTH_WORKDIR):
+	mkdir -p $@
+
+.PHONY: echo-ghdl-flags echo-sim-run-flags
+echo-ghdl-flags:
+	@echo $(GHDL_FLAGS)
+
+echo-sim-run-flags:
+	@echo $(SIM_RUN_FLAGS)
diff --git a/Makefile.symbiflow b/Makefile.symbiflow
new file mode 100644
index 0000000..a8d23d3
--- /dev/null
+++ b/Makefile.symbiflow
@@ -0,0 +1,23 @@
+SYNTH_OUTPUT_FILE = $(SYNTH_WORKDIR)/$(YOSYS_MODULE_NAME).eblif
+
+$(SYNTH_WORKDIR)/%.il: $(VHDL_FILES) $(VERILOG_FILES) | $(SYNTH_WORKDIR) $(GHDL_WORKDIR)/work-obj$(VHDL_STD).cf
+	$(GHDL) make $(GHDL_FLAGS) $(SYNTH_ENTITY)
+	$(YOSYS) -m $(GHDL_YOSYS_PLUGIN) -p 'read_verilog -defer $(VERILOG_FILES); ghdl $(GHDL_FLAGS) $(SYNTH_ENTITY); chformal -remove; check -assert; write_rtlil $@'
+
+$(SYNTH_WORKDIR)/%.eblif: $(SYNTH_WORKDIR)/%.il $(XDC)
+	cd $(SYNTH_WORKDIR) && symbiflow_synth -d artix7 -t $* -v $< -p $(PART) -x $(XDC)
+
+$(SYNTH_WORKDIR)/%.net: $(SYNTH_WORKDIR)/%.eblif
+	cd $(SYNTH_WORKDIR) && symbiflow_pack -d xc7a50t_test -e $<
+
+$(SYNTH_WORKDIR)/%.place: $(SYNTH_WORKDIR)/%.eblif $(SYNTH_WORKDIR)/%.net
+	cd $(SYNTH_WORKDIR) && symbiflow_place -d xc7a50t_test -e $< -n $(word 2,$^) -P $(PART)
+
+$(SYNTH_WORKDIR)/%.route: $(SYNTH_WORKDIR)/%.eblif $(SYNTH_WORKDIR)/%.place
+	cd $(SYNTH_WORKDIR) && symbiflow_route -d xc7a50t_test -e $<
+
+$(SYNTH_WORKDIR)/%.fasm: $(SYNTH_WORKDIR)/%.eblif $(SYNTH_WORKDIR)/%.route
+	cd $(SYNTH_WORKDIR) && symbiflow_write_fasm -d xc7a50t_test -e $<
+
+$(SYNTH_WORKDIR)/%.bit: $(SYNTH_WORKDIR)/%.fasm
+	cd $(SYNTH_WORKDIR) && symbiflow_write_bitstream -d artix7 -f $< -p $(PART) -b $@
diff --git a/arty_a7_35.xdc b/arty_a7_35.xdc
new file mode 100644
index 0000000..d4106fb
--- /dev/null
+++ b/arty_a7_35.xdc
@@ -0,0 +1,225 @@
+set_property LOC E3   [get_ports clock_100mhz]
+set_property LOC A9   [get_ports uart_rx]
+set_property LOC D10  [get_ports uart_tx]
+set_property LOC C2   [get_ports n_reset]
+set_property LOC G6   [get_ports {led0[2]}]
+set_property LOC F6   [get_ports {led0[1]}]
+set_property LOC E1   [get_ports {led0[0]}]
+set_property LOC G3   [get_ports {led1[2]}]
+set_property LOC J4   [get_ports {led1[1]}]
+set_property LOC G4   [get_ports {led1[0]}]
+set_property LOC J3   [get_ports {led2[2]}]
+set_property LOC J2   [get_ports {led2[1]}]
+set_property LOC H4   [get_ports {led2[0]}]
+set_property LOC K1   [get_ports {led3[2]}]
+set_property LOC H6   [get_ports {led3[1]}]
+set_property LOC K2   [get_ports {led3[0]}]
+set_property LOC A8   [get_ports {switches[0]}]
+set_property LOC C11  [get_ports {switches[1]}]
+set_property LOC C10  [get_ports {switches[2]}]
+set_property LOC A10  [get_ports {switches[3]}]
+set_property LOC D9   [get_ports {buttons[0]}]
+set_property LOC C9   [get_ports {buttons[1]}]
+set_property LOC B9   [get_ports {buttons[2]}]
+set_property LOC B8   [get_ports {buttons[3]}]
+set_property LOC H5   [get_ports {leds_simple[0]}]
+set_property LOC J5   [get_ports {leds_simple[1]}]
+set_property LOC T9   [get_ports {leds_simple[2]}]
+set_property LOC T10  [get_ports {leds_simple[3]}]
+
+set_property LOC K13  [get_ports mii_mdio]
+set_property LOC F16  [get_ports mii_mdc]
+set_property LOC F15  [get_ports mii_rx_clk]
+set_property LOC C17  [get_ports mii_rx_er]
+set_property LOC G16  [get_ports mii_rx_dv]
+set_property LOC D18  [get_ports {mii_rx_data[0]}]
+set_property LOC E17  [get_ports {mii_rx_data[1]}]
+set_property LOC E18  [get_ports {mii_rx_data[2]}]
+set_property LOC G17  [get_ports {mii_rx_data[3]}]
+set_property LOC H16  [get_ports mii_tx_clk]
+set_property LOC H15  [get_ports mii_tx_en]
+set_property LOC H14  [get_ports {mii_tx_data[0]}]
+set_property LOC J14  [get_ports {mii_tx_data[1]}]
+set_property LOC J13  [get_ports {mii_tx_data[2]}]
+set_property LOC H17  [get_ports {mii_tx_data[3]}]
+set_property LOC D17  [get_ports mii_col]
+set_property LOC G14  [get_ports mii_crs]
+set_property LOC C16  [get_ports mii_n_reset]
+set_property LOC G18  [get_ports mii_clk_25mhz]
+
+set_property LOC G13  [get_ports {pmod_a[0]}]
+set_property LOC B11  [get_ports {pmod_a[1]}]
+set_property LOC A11  [get_ports {pmod_a[2]}]
+set_property LOC D12  [get_ports {pmod_a[3]}]
+set_property LOC D13  [get_ports {pmod_a[4]}]
+set_property LOC B18  [get_ports {pmod_a[5]}]
+set_property LOC A18  [get_ports {pmod_a[6]}]
+set_property LOC K16  [get_ports {pmod_a[7]}]
+set_property LOC E15  [get_ports {pmod_b[0]}]
+set_property LOC E16  [get_ports {pmod_b[1]}]
+set_property LOC D15  [get_ports {pmod_b[2]}]
+set_property LOC C15  [get_ports {pmod_b[3]}]
+set_property LOC J17  [get_ports {pmod_b[4]}]
+set_property LOC J18  [get_ports {pmod_b[5]}]
+set_property LOC K15  [get_ports {pmod_b[6]}]
+set_property LOC J15  [get_ports {pmod_b[7]}]
+set_property LOC U12  [get_ports {pmod_c[0]}]
+set_property LOC V12  [get_ports {pmod_c[1]}]
+set_property LOC V10  [get_ports {pmod_c[2]}]
+set_property LOC V11  [get_ports {pmod_c[3]}]
+set_property LOC U14  [get_ports {pmod_c[4]}]
+set_property LOC V14  [get_ports {pmod_c[5]}]
+set_property LOC T13  [get_ports {pmod_c[6]}]
+set_property LOC U13  [get_ports {pmod_c[7]}]
+set_property LOC D4   [get_ports {pmod_d[0]}]
+set_property LOC D3   [get_ports {pmod_d[1]}]
+set_property LOC F4   [get_ports {pmod_d[2]}]
+set_property LOC F3   [get_ports {pmod_d[3]}]
+set_property LOC E2   [get_ports {pmod_d[4]}]
+set_property LOC D2   [get_ports {pmod_d[5]}]
+set_property LOC H2   [get_ports {pmod_d[6]}]
+set_property LOC G2   [get_ports {pmod_d[7]}]
+
+set_property LOC V15  [get_ports {ck_dig_l[0]}]
+set_property LOC U16  [get_ports {ck_dig_l[1]}]
+set_property LOC P14  [get_ports {ck_dig_l[2]}]
+set_property LOC T11  [get_ports {ck_dig_l[3]}]
+set_property LOC R12  [get_ports {ck_dig_l[4]}]
+set_property LOC T14  [get_ports {ck_dig_l[5]}]
+set_property LOC T15  [get_ports {ck_dig_l[6]}]
+set_property LOC T16  [get_ports {ck_dig_l[7]}]
+set_property LOC N15  [get_ports {ck_dig_l[8]}]
+set_property LOC M16  [get_ports {ck_dig_l[9]}]
+set_property LOC V17  [get_ports {ck_dig_l[10]}]
+set_property LOC U18  [get_ports {ck_dig_l[11]}]
+set_property LOC R17  [get_ports {ck_dig_l[12]}]
+set_property LOC P17  [get_ports {ck_dig_l[13]}]
+
+set_property LOC U11  [get_ports {ck_dig_h[0]}]
+set_property LOC V16  [get_ports {ck_dig_h[1]}]
+set_property LOC M13  [get_ports {ck_dig_h[2]}]
+set_property LOC R10  [get_ports {ck_dig_h[3]}]
+set_property LOC R11  [get_ports {ck_dig_h[4]}]
+set_property LOC R13  [get_ports {ck_dig_h[5]}]
+set_property LOC R15  [get_ports {ck_dig_h[6]}]
+set_property LOC P15  [get_ports {ck_dig_h[7]}]
+set_property LOC R16  [get_ports {ck_dig_h[8]}]
+set_property LOC N16  [get_ports {ck_dig_h[9]}]
+set_property LOC N14  [get_ports {ck_dig_h[10]}]
+set_property LOC U17  [get_ports {ck_dig_h[11]}]
+set_property LOC T18  [get_ports {ck_dig_h[12]}]
+set_property LOC R18  [get_ports {ck_dig_h[13]}]
+set_property LOC P18  [get_ports {ck_dig_h[14]}]
+set_property LOC N17  [get_ports {ck_dig_h[15]}]
+
+set_property IOSTANDARD LVCMOS33 [get_ports clock_100mhz]
+set_property IOSTANDARD LVCMOS33 [get_ports uart_rx]
+set_property IOSTANDARD LVCMOS33 [get_ports uart_tx]
+set_property IOSTANDARD LVCMOS33 [get_ports n_reset]
+set_property IOSTANDARD LVCMOS33 [get_ports {led0[2]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {led0[1]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {led0[0]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {led1[2]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {led1[1]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {led1[0]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {led2[2]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {led2[1]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {led2[0]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {led3[2]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {led3[1]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {led3[0]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {switches[0]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {switches[1]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {switches[2]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {switches[3]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {buttons[0]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {buttons[1]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {buttons[2]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {buttons[3]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {leds_simple[0]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {leds_simple[1]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {leds_simple[2]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {leds_simple[3]}]
+set_property IOSTANDARD LVCMOS33 [get_ports mii_mdio]
+set_property IOSTANDARD LVCMOS33 [get_ports mii_mdc]
+set_property IOSTANDARD LVCMOS33 [get_ports mii_rx_clk]
+set_property IOSTANDARD LVCMOS33 [get_ports mii_rx_er]
+set_property IOSTANDARD LVCMOS33 [get_ports mii_rx_dv]
+set_property IOSTANDARD LVCMOS33 [get_ports {mii_rx_data[0]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {mii_rx_data[1]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {mii_rx_data[2]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {mii_rx_data[3]}]
+set_property IOSTANDARD LVCMOS33 [get_ports mii_tx_clk]
+set_property IOSTANDARD LVCMOS33 [get_ports mii_tx_en]
+set_property IOSTANDARD LVCMOS33 [get_ports {mii_tx_data[0]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {mii_tx_data[1]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {mii_tx_data[2]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {mii_tx_data[3]}]
+set_property IOSTANDARD LVCMOS33 [get_ports mii_col]
+set_property IOSTANDARD LVCMOS33 [get_ports mii_crs]
+set_property IOSTANDARD LVCMOS33 [get_ports mii_n_reset]
+set_property IOSTANDARD LVCMOS33 [get_ports mii_clk_25mhz]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_a[0]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_a[1]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_a[2]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_a[3]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_a[4]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_a[5]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_a[6]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_a[7]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_b[0]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_b[1]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_b[2]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_b[3]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_b[4]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_b[5]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_b[6]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_b[7]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_c[0]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_c[1]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_c[2]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_c[3]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_c[4]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_c[5]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_c[6]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_c[7]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_d[0]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_d[1]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_d[2]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_d[3]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_d[4]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_d[5]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_d[6]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {pmod_d[7]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {ck_dig_l[0]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {ck_dig_l[1]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {ck_dig_l[2]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {ck_dig_l[3]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {ck_dig_l[4]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {ck_dig_l[5]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {ck_dig_l[6]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {ck_dig_l[7]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {ck_dig_l[8]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {ck_dig_l[9]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {ck_dig_l[10]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {ck_dig_l[11]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {ck_dig_l[12]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {ck_dig_l[13]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {ck_dig_h[0]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {ck_dig_h[1]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {ck_dig_h[2]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {ck_dig_h[3]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {ck_dig_h[4]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {ck_dig_h[5]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {ck_dig_h[6]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {ck_dig_h[7]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {ck_dig_h[8]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {ck_dig_h[9]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {ck_dig_h[10]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {ck_dig_h[11]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {ck_dig_h[12]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {ck_dig_h[13]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {ck_dig_h[14]}]
+set_property IOSTANDARD LVCMOS33 [get_ports {ck_dig_h[15]}]
+
+create_clock -name clk_100mhz -period 10.000 [get_nets clock_100mhz]
diff --git a/gen_liteeth.py b/gen_liteeth.py
new file mode 100755
index 0000000..f43ee95
--- /dev/null
+++ b/gen_liteeth.py
@@ -0,0 +1,267 @@
+#!/usr/bin/env python3
+
+#
+# This file is part of LiteEth.
+#
+# Copyright (c) 2015-2022 Florent Kermarrec <florent@enjoy-digital.fr>
+# Copyright (c) 2020 Xiretza <xiretza@xiretza.xyz>
+# Copyright (c) 2020 Stefan Schrijvers <ximin@ximinity.net>
+# SPDX-License-Identifier: BSD-2-Clause
+
+import argparse
+import os
+import yaml
+
+from migen import *
+
+from litex.build.generic_platform import *
+from litex.build.xilinx.platform import XilinxPlatform
+from litex.build.lattice.platform import LatticePlatform
+
+from litex.soc.interconnect import wishbone
+from litex.soc.integration.soc_core import *
+from litex.soc.integration.builder import *
+from litex.soc.integration.soc import SoCRegion
+
+from liteeth.common import *
+
+from liteeth import phy as liteeth_phys
+from liteeth.mac import LiteEthMAC
+from liteeth.core import LiteEthUDPIPCore
+
+# IOs ----------------------------------------------------------------------------------------------
+
+MAC_ADDRESS = 0x00183e02a914
+CLK_FREQ = int(125e6)
+
+_io = [
+    # Clk / Rst
+    ("sys_clock", 0, Pins(1)),
+    ("sys_reset", 1, Pins(1)),
+
+    # IP/MAC Address.
+    ("mac_address", 0, Pins(48)),
+    ("ip_address",  0, Pins(32)),
+
+    # Interrupt
+    ("interrupt", 0, Pins(1)),
+
+    # MII PHY Pads
+    ("mii_eth_clocks", 0,
+        Subsignal("tx", Pins(1)),
+        Subsignal("rx", Pins(1)),
+     ),
+    ("mii_eth", 0,
+        Subsignal("rst_n",   Pins(1)),
+        Subsignal("mdio",    Pins(1)),
+        Subsignal("mdc",     Pins(1)),
+        Subsignal("rx_dv",   Pins(1)),
+        Subsignal("rx_er",   Pins(1)),
+        Subsignal("rx_data", Pins(4)),
+        Subsignal("tx_en",   Pins(1)),
+        Subsignal("tx_data", Pins(4)),
+        Subsignal("col",     Pins(1)),
+        Subsignal("crs",     Pins(1))
+     ),
+
+    # RMII PHY Pads
+    ("rmii_eth_clocks", 0,
+        Subsignal("ref_clk", Pins(1))
+     ),
+    ("rmii_eth", 0,
+        Subsignal("rst_n",   Pins(1)),
+        Subsignal("rx_data", Pins(2)),
+        Subsignal("crs_dv",  Pins(1)),
+        Subsignal("tx_en",   Pins(1)),
+        Subsignal("tx_data", Pins(2)),
+        Subsignal("mdc",     Pins(1)),
+        Subsignal("mdio",    Pins(1)),
+     ),
+
+    # GMII PHY Pads
+    ("gmii_eth_clocks", 0,
+        Subsignal("tx",  Pins(1)),
+        Subsignal("gtx", Pins(1)),
+        Subsignal("rx",  Pins(1))
+     ),
+    ("gmii_eth", 0,
+        Subsignal("rst_n",   Pins(1)),
+        Subsignal("int_n",   Pins(1)),
+        Subsignal("mdio",    Pins(1)),
+        Subsignal("mdc",     Pins(1)),
+        Subsignal("rx_dv",   Pins(1)),
+        Subsignal("rx_er",   Pins(1)),
+        Subsignal("rx_data", Pins(8)),
+        Subsignal("tx_en",   Pins(1)),
+        Subsignal("tx_er",   Pins(1)),
+        Subsignal("tx_data", Pins(8)),
+        Subsignal("col",     Pins(1)),
+        Subsignal("crs",     Pins(1))
+     ),
+
+    # RGMII PHY Pads
+    ("rgmii_eth_clocks", 0,
+        Subsignal("tx", Pins(1)),
+        Subsignal("rx", Pins(1))
+     ),
+    ("rgmii_eth", 0,
+        Subsignal("rst_n",   Pins(1)),
+        Subsignal("int_n",   Pins(1)),
+        Subsignal("mdio",    Pins(1)),
+        Subsignal("mdc",     Pins(1)),
+        Subsignal("rx_ctl",  Pins(1)),
+        Subsignal("rx_data", Pins(4)),
+        Subsignal("tx_ctl",  Pins(1)),
+        Subsignal("tx_data", Pins(4))
+     ),
+]
+
+
+def get_udp_port_ios(name, data_width):
+    return [
+        (f"{name}", 0,
+            Subsignal("ip_address", Pins(32)),
+
+            # Sink.
+            Subsignal("sink_valid", Pins(1)),
+            Subsignal("sink_last",  Pins(1)),
+            Subsignal("sink_ready", Pins(1)),
+            Subsignal("sink_data",  Pins(data_width)),
+
+            # Source.
+            Subsignal("source_valid", Pins(1)),
+            Subsignal("source_last",  Pins(1)),
+            Subsignal("source_ready", Pins(1)),
+            Subsignal("source_data",  Pins(data_width)),
+         ),
+    ]
+
+
+class PHYCore(SoCMini):
+    def __init__(self, platform):
+        super().__init__(platform, clk_freq=CLK_FREQ)
+
+        # CRG --------------------------------------------------------------------------------------
+        self.submodules.crg = CRG(
+            platform.request("sys_clock"),
+            platform.request("sys_reset")
+        )
+
+        # PHY --------------------------------------------------------------------------------------
+        phy = liteeth_phys.LiteEthPHYRMII
+        ethphy = phy(
+            refclk_cd=None,
+            clock_pads=platform.request("rmii_eth_clocks"),
+            pads=platform.request("rmii_eth")
+        )
+        self.submodules.ethphy = ethphy
+
+        # Timing constaints.
+        # Generate timing constraints to ensure the "keep" attribute is properly set on the various
+        # clocks. This also adds the constraints to the generated .xdc that can then be "imported"
+        # in the project using the core.
+        eth_rx_clk = getattr(ethphy, "crg", ethphy).cd_eth_rx.clk
+        eth_tx_clk = getattr(ethphy, "crg", ethphy).cd_eth_tx.clk
+        from liteeth.phy.model import LiteEthPHYModel
+        if not isinstance(ethphy, LiteEthPHYModel):
+            self.platform.add_period_constraint(
+                eth_rx_clk,
+                1e9/phy.rx_clk_freq
+            )
+            self.platform.add_period_constraint(
+                eth_tx_clk,
+                1e9/phy.tx_clk_freq
+            )
+            self.platform.add_false_path_constraints(
+                self.crg.cd_sys.clk,
+                eth_rx_clk,
+                eth_tx_clk
+            )
+
+
+class UDPCore(PHYCore):
+    def __init__(self, platform):
+        from liteeth.frontend.stream import LiteEthUDPStreamer
+
+        super().__init__(platform)
+
+        ip_address = platform.request("ip_address")
+
+        # Core
+        self.submodules.core = LiteEthUDPIPCore(
+            self.ethphy,
+            mac_address=MAC_ADDRESS,
+            ip_address=ip_address,
+            clk_freq=CLK_FREQ,
+            dw=8,
+            with_sys_datapath=False,
+        )
+
+        # DHCP port
+        data_width = 32
+
+        platform.add_extension(get_udp_port_ios(
+            "dhcp",
+            data_width=data_width,
+        ))
+        dhcp_ios = platform.request("dhcp")
+
+        dhcp_streamer = LiteEthUDPStreamer(
+            self.core.udp,
+            ip_address=dhcp_ios.ip_address,
+            udp_port=67,
+            data_width=data_width,
+            tx_fifo_depth=64,
+            rx_fifo_depth=64
+        )
+        self.submodules += dhcp_streamer
+
+        self.comb += [
+            # Connect UDP Sink IOs to UDP Steamer.
+            dhcp_streamer.sink.valid.eq(dhcp_ios.sink_valid),
+            dhcp_streamer.sink.last.eq(dhcp_ios.sink_last),
+            dhcp_ios.sink_ready.eq(dhcp_streamer.sink.ready),
+            dhcp_streamer.sink.data.eq(dhcp_ios.sink_data),
+
+            # Connect UDP Streamer to UDP Source IOs.
+            dhcp_ios.source_valid.eq(dhcp_streamer.source.valid),
+            dhcp_ios.source_last.eq(dhcp_streamer.source.last),
+            dhcp_streamer.source.ready.eq(dhcp_ios.source_ready),
+            dhcp_ios.source_data.eq(dhcp_streamer.source.data),
+        ]
+
+# Build --------------------------------------------------------------------------------------------
+
+
+def main():
+    parser = argparse.ArgumentParser(
+        description="splink LiteEth core generator"
+    )
+    builder_args(parser)
+    parser.set_defaults(output_dir="build")
+    args = parser.parse_args()
+
+    # Generate core --------------------------------------------------------------------------------
+    platform = XilinxPlatform(
+        "xc7a35ticsg324-1L",
+        io=[],
+        toolchain="symbiflow"
+    )
+    platform.add_extension(_io)
+
+    soc = UDPCore(platform)
+
+    builder_arguments = builder_argdict(args)
+    builder_arguments["compile_gateware"] = False
+    if builder_arguments["csr_csv"] is None:
+        builder_arguments["csr_csv"] = os.path.join(
+            builder_arguments["output_dir"],
+            "csr.csv"
+        )
+
+    builder = Builder(soc, **builder_arguments)
+    builder.build(build_name="liteeth_core")
+
+
+if __name__ == "__main__":
+    main()
diff --git a/vhdl/arty_a7.vhdl b/vhdl/arty_a7.vhdl
new file mode 100644
index 0000000..93006d3
--- /dev/null
+++ b/vhdl/arty_a7.vhdl
@@ -0,0 +1,82 @@
+library ieee;
+use ieee.std_logic_1164.all,
+    ieee.numeric_std.all;
+
+entity arty_a7 is
+	generic (
+		IS_SIMULATION : std_logic := '0'
+	);
+	port (
+		n_reset     : in std_logic;
+		buttons     : in std_logic_vector(3 downto 0);
+		switches    : in std_logic_vector(3 downto 0);
+		leds_simple : out std_logic_vector(3 downto 0);
+		led0, led1, led2, led3 : out std_logic_vector(2 downto 0);
+
+		-- Pmod connectors - A+D standard, B+C high-speed.
+		-- Defined as inputs by default for safety, change
+		-- when necessary
+		pmod_a : in std_logic_vector(7 downto 0);
+		pmod_b : in std_logic_vector(7 downto 0);
+		pmod_c : in std_logic_vector(7 downto 0);
+		pmod_d : in std_logic_vector(7 downto 0);
+
+		clock_100mhz : in std_logic;
+
+		uart_rx : in std_logic;
+		uart_tx : out std_logic;
+
+		mii_clk_25mhz : out std_logic;
+		mii_n_reset   : out std_logic;
+		mii_mdio      : inout std_logic;
+		mii_mdc       : out std_logic;
+		mii_rx_clk    : in std_logic;
+		mii_rx_er     : in std_logic;
+		mii_rx_dv     : in std_logic;
+		mii_rx_data   : in std_logic_vector(3 downto 0);
+		mii_tx_clk    : in std_logic;
+		mii_tx_en     : out std_logic;
+		mii_tx_data   : out std_logic_vector(3 downto 0);
+		mii_col       : in std_logic;
+		mii_crs       : in std_logic;
+
+		ck_dig_l : inout std_logic_vector(13 downto 0);
+		ck_dig_h : inout std_logic_vector(41 downto 26)
+	);
+end arty_a7;
+
+architecture a of arty_a7 is
+	constant NUM_DRIVERS: positive := 16;
+	signal drivers: std_logic_vector(NUM_DRIVERS-1 downto 0);
+begin
+	--leds_simple <= (others => '0');
+	led0 <= (others => '0');
+	led1 <= (others => '0');
+	led2 <= (others => '0');
+	led3 <= (others => '0');
+
+	uart_tx <= '0';
+
+	mii_clk_25mhz <= '0';
+	mii_n_reset <= '0';
+	mii_mdio <= 'Z';
+	mii_mdc <= '0';
+	mii_tx_en <= '0';
+	mii_tx_data <= (others => '0');
+
+	ck_dig_l <= (others => 'Z');
+	ck_dig_h <= (others => 'Z');
+
+	leds_simple <= drivers(3 downto 0);
+
+	splink: entity work.splink
+		generic map (
+			NUM_DRIVERS => NUM_DRIVERS
+		)
+		port map (
+			clk => clock_100mhz,
+			reset => not n_reset,
+
+			drivers => drivers
+		);
+end architecture;
diff --git a/vhdl/splink.vhdl b/vhdl/splink.vhdl
new file mode 100644
index 0000000..32bf7da
--- /dev/null
+++ b/vhdl/splink.vhdl
@@ -0,0 +1,36 @@
+library ieee;
+use ieee.std_logic_1164.all;
+use ieee.numeric_std.all;
+
+entity splink is
+	generic (
+		NUM_DRIVERS : positive := 16;
+		ROWS : positive := 100;
+		COLS : positive := 100
+	);
+	port (
+		clk : in std_logic;
+		reset : in std_logic;
+
+		drivers : out std_logic_vector(NUM_DRIVERS-1 downto 0)
+	);
+end entity;
+
+architecture a of splink is
+	signal count2: unsigned(3 downto 0);
+	signal count: natural range 0 to 10000000;
+begin
+	process(clk)
+	begin
+		if rising_edge(clk) then
+			if count = 10000000 then
+				count <= 0;
+				count2 <= count2 + 1;
+			else
+				count <= count + 1;
+			end if;
+		end if;
+	end process;
+
+	drivers <= (15 downto 4 => '0') & std_logic_vector(count2);
+end architecture;