Differential I/O Connectors - Xilinx Spartan-3A User Manual

Chapter 15: Expansion Connectors

Differential I/O Connectors

The Spartan-3A/3AN Starter Kit board includes stake pin headers with excellent signal
integrity and matched impedance traces to demonstrate high-performance differential
I/O. Each differential pair supports approximately 600 Mbits per second (Mbps) data
rates. All I/O pairs support differential input termination (DIFF_TERM) as described in
the Spartan-3A and Spartan-3AN data sheets.
The board is primarily designed to support loopback operations using a standard 34-pin
socket-to-socket cable.
The two differential I/O headers, shown in
stake pins arrange on 0.1-inch centers. The headers are not keyed. Ground pins are
interspersed with the signal pins for improved signal integrity over any attached cable.
Power is also supplied, via the nominally 3.3V rail, labeled VCCO_012. The power
connectors are for potential daughter cards that plug into the connector.
The J15 connector is primarily designed to transmit output data while the J2 connector is
primarily designed to receive input data. However, both headers are equally good at
transmitting differential data. The "Receive" header does have special provisions for
capturing the receive clock input.
The pin assignment for the J2 "Receive" connector appears in
The FPGA ball assignment is listed in parentheses.
Table 15-2: Receive" Header (J2)
2 4 6 8
RXN_0
GND GND GND
(B4)
RXP_0
GND GND GND
(A4)
1 3 5 7
The pin assignment for the J15 "Transmit" connector appears in
Table
Table 15-3: Transmit" Header (J15)
2 4 6 8
TXN_0
GND GND GND
(AA3)
TXP_0
GND GND GND
(AB2)
1 3 5 7
126
10 12 14 16
RXN_1 RXN_2
GND 3.3V 3.3V 3.3V
(A5) (A6)
RXP_1 RXP_2
GND 3.3V 3.3V 3.3V
(B6) (A7)
9 11 13 15
15-4. The FPGA ball assignment is listed in parentheses.
10 12 14 16
TXN_1 TXN_2
GND 3.3V 3.3V 3.3V
(AA4) (AB6)
TXP_1 TXP_2
GND 3.3V 3.3V 3.3V
(AB3) (AA6)
9 11 13 15
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Figure 15-1, page
18 20 22 24
RXN_3
GND
(A8)
RXP_3
GND
(A9)
17 19 21 23
18 20 22 24
TXN_3
GND
(AB7)
TXP_3
GND
(Y7)
17 19 21 23
Spartan-3A/3AN Starter Kit Board User Guide
121, consist of a 2x17 array of
Table 15-2 and in Table
26 28 30 32
RX_
RXN_4
GND GND GND
CLK_N
(C10)
(A11)
RX_
RXP_4
GND GND GND
CLK_P
(A10)
(A12)
25 27 29 31
Table 15-3 and in
26 28 30 32
TX_
TXN_4
GND GND GND
CLK_N
(AB8)
(AB10)
TX_
TXP_4
GND GND GND
CLK_P
(AA8)
(AA10)
25 27 29 31
UG334 (v1.0) May 28, 2007
R
15-4.
34
33
34
33