--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/duart28c/src/vsrc/USB_block.v	Wed Jul 29 07:08:28 2020 +0000
@@ -0,0 +1,67 @@
+/*
+ * This module encapsulates the USB connector, the FT2232D block and
+ * the glue components between them.
+ */
+
+module USB_block (GND, P_5V, VCCIOA, VCCIOB,
+		  ADBUS, ACBUS, SI_WUA, BDBUS, BCBUS, SI_WUB, PWREN);
+
+output GND, P_5V;
+
+input VCCIOA, VCCIOB;
+inout [7:0] ADBUS, BDBUS;
+inout [3:0] ACBUS, BCBUS;
+input SI_WUA, SI_WUB;
+output PWREN;
+
+/* interconnecting wires */
+
+wire VBUS;
+wire DM_connector_side, DM_chip_side;
+wire DP_connector_side, DP_chip_side;
+wire RSTOUT;
+
+usb_conn conn  (.GND(GND),
+		.VBUS(VBUS),
+		.Dminus(DM_connector_side),
+		.Dplus(DP_connector_side),
+		.ID()	/* no connect */
+	);
+
+/* ferrite bead on the power supply */
+
+inductor VBUS_ferrite (VBUS, P_5V);
+
+/* series resistors on USB data lines */
+
+resistor DM_series_R (DM_connector_side, DM_chip_side);
+resistor DP_series_R (DP_connector_side, DP_chip_side);
+
+/* we can now bring in the FT2232D block */
+
+FT2232D_block FT2232D  (.GND(GND),
+			.VCC(P_5V),
+			.VCCIOA(VCCIOA),
+			.VCCIOB(VCCIOB),
+			.USBDP(DP_chip_side),
+			.USBDM(DM_chip_side),
+			.RESET(P_5V),
+			.RSTOUT(RSTOUT),
+			.PWREN(PWREN),
+			.ADBUS(ADBUS),
+			.ACBUS(ACBUS),
+			.SI_WUA(SI_WUA),
+			.BDBUS(BDBUS),
+			.BCBUS(BCBUS),
+			.SI_WUB(SI_WUB)
+	);
+
+resistor DP_pullup_R (DP_chip_side, RSTOUT);
+
+/* power bypass caps */
+
+capacitor VBUS_in_cap (VBUS, GND);
+capacitor P_5V_cap (P_5V, GND);
+capacitor P_5V_cap2 (P_5V, GND);
+
+endmodule