Nexys 3™ FPGA Board Reference Manual
Copyright Digilent, Inc. All rights reserved.
Other product and company names mentioned may be trademarks of their respective owners.
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All FPGA pins routed to the VHDC connector are located in FPGA I/O bank0. The FPGA's bank0 I/O power supply
pins and the VHDC connector's four Vcc pins are connected together by a small, segregated power supply plane in
the PCB. This sub-plane can be connected to 2.5V or 3.3V, depending on the position of jumper JP8. This
arrangement allows peripheral boards and the FPGA to share the same Vcc and signaling voltage across the
connector, whether it be 3.3V or 2.5V.
The unregulated board voltage VU5V0 (nominally 5V) is also routed to four other VHDC pins, supplying up to 1A of
additional current to peripheral boards. A second jumper (JP4) allows the unregulated board voltage to be
disconnected from the VHDC connector if desired.
All I/O's to the VHDC connector are routed as matched
pairs to support LVDS signaling, commonly powered at
2.5V. The connector uses a symmetrical pinout (as
reflected around the connector's vertical axis) so that
peripheral boards as well as other system boards can be
connected. Connector pins 15 and 49 are routed to FPGA
clock input pins.
VU
Pin 34
Pin 68
Pin 1:IO1-P
Pin 35:IO1-N
VCC
10 Matched Pairs
10 Matched Pairs
Clock Inputs
VHDC Connector Pinout
IO1-P: B2
IO1-N: A2
IO11-P: C10
IO11-N: A10
IO2-P: D6
IO2-N: C6
IO12-P: G9
IO12-N: F9
IO3-P: B3
IO3-N: A3
IO13-P: B11
IO13-N: A11
IO4-P: B4
IO4-N: A4
IO14-P: B12
IO14-N: A12
IO5-P: C5
IO5-N: A5
IO15-P: C13
IO15-N: A13
IO6-P: B6
IO6-N: A6
IO16-P: B14
IO16-N: A14
IO7-P: C7
IO7-N: A7
IO17-P: F13
IO17-N: E13
IO8-P: D8
IO8-N: C8
IO18-P: C15
IO18-N: A15
IO9-P: B9
IO9-N: A9
IO19-P: D14
IO19-N: C14
IO10-P: D11
IO10-N: C11
IO20-P: B16
IO20-N: A16
10.2 Pmod Ports
Pmod ports are 2x6 right-angle, 100-mil female connectors that mate with standard 2x6 pin headers available from
a variety of catalog distributors. Each 12-pin Pmod port provides two 3.3V VCC signals (pins 6 and 12), two Ground
signals (pins 5 and 11), and eight logic signals. VCC and Ground pins can deliver up to 1A of current. Pmod data
3.3V 2.5V
Spartan 6
VHDC
VCCO
20 Matched Pairs
JP8
VU5V0
Bank0
JP4
