view venus/src/usb/usb_domain_bctl.v @ 36:c1256c8757c3

eliminate R209 and tie Iota VLMEM directly to UPR We already eliminated R210 (VLMEM pull-down option) earlier, because our simplified LCD power supply and reset line wiring is incompatible with 1.8V MEMIF. But with VLMEM always needing to be high, a pull-up resistor offers no advantage over a direct tie to UPR, so let's eliminate the superfluous resistor.
author Mychaela Falconia <falcon@freecalypso.org>
date Mon, 22 Nov 2021 19:19:59 +0000
parents 4722b265cb8c
children 9309cebe07b8
line wrap: on
line source

/*
 * This module encapsulates the USB domain circuit for boot control.
 */

module usb_domain_bctl (GND, P_3V3, ChanB_RTS, ChanB_DTR, CTL1_out, CTL2_out);

input GND, P_3V3;
input ChanB_RTS, ChanB_DTR;
output CTL1_out, CTL2_out;

/* pull-up resistors on FT2232D outputs */

resistor ChanB_RTS_pullup (ChanB_RTS, P_3V3);
resistor ChanB_DTR_pullup (ChanB_DTR, P_3V3);

/* open drain buffers */

logic_ic_common od_buf_common ( .Vcc(P_3V3),
				.GND(GND)
	);

capacitor od_buf_bypass_cap (P_3V3, GND);

buffer_slot_basic buf_CTL1 (.A(ChanB_RTS), .Y(CTL1_out));
buffer_slot_basic buf_CTL2 (.A(ChanB_DTR), .Y(CTL2_out));

endmodule