--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/venus/src/periph/jtag_if.v	Sat Nov 20 04:32:50 2021 +0000
@@ -0,0 +1,55 @@
+/*
+ * This Verilog module captures our JTAG interface circuit, copied from
+ * Leonardo and FCDEV3B.  Unlike FCDEV3B, for the present FC Venus version
+ * we omit TI's non-understood EMU0/1 signals.  In our defense, Leonardo
+ * schematics also show EMU0/1 as unconnected, with only the JTAG scan chain
+ * and XDS_RESET brought out.
+ */
+
+module jtag_if (GND, Vio, nTESTRESET, TDI, TCK, TMS, TDO);
+
+input GND, Vio;
+
+inout nTESTRESET;
+
+output TDI, TCK, TMS;
+input TDO;
+
+wire XDS_RESET, between_transistors;
+
+header_14pin connector (.pin_1(TMS),
+			.pin_2(XDS_RESET),
+			.pin_3(TDI),
+			.pin_4(GND),
+			.pin_5(Vio),
+			.pin_6(),	/* keying position */
+			.pin_7(TDO),
+			.pin_8(GND),
+			.pin_9(TCK),
+			.pin_10(GND),
+			.pin_11(TCK),
+			.pin_12(GND),
+			.pin_13(),	/* EMU0 omitted */
+			.pin_14()	/* EMU1 omitted */
+	);
+
+capacitor C363 (Vio, GND);
+
+/* pull-up/down resistors */
+resistor_slot R361A (TCK, GND);
+/* skipping TDO (R361B) */
+resistor_slot R361C (TDI, Vio);
+resistor_slot R361D (TMS, Vio);
+
+/* reset circuit */
+capacitor C335 (Vio, XDS_RESET);
+transistor_slot PNP (.E(Vio),
+		     .B(XDS_RESET),
+		     .C(between_transistors)
+	);
+transistor_slot NPN (.E(GND),
+		     .B(between_transistors),
+		     .C(nTESTRESET)
+	);
+
+endmodule