Spartan-3A/3AN FPGA Starter Kit Board User Guide
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125
UG334 (v1.1) June 19, 2008
Differential I/O Connectors
R
Table 15-4
provides further detail on the pin assignment, including the differential pair
association, the FPGA ball assignment, and the connecting header pin.
Using Differential Inputs
LVDS and RSDS differential inputs require input termination. Two options are generally
available. The first option is to use external termination resistors, as shown in
Figure 15-4a
.
External input termination resistors are not provided on the differential I/O pins.
The second option, called on-chip differential termination, is highlighted on
the Spartan-
3A/3AN Starter Kit board (see
Figure 15-4b
). This feature uses the DIFF_TERM attribute
available on differential I/O signals. Each differential I/O pin includes a circuit that
Table 15-4:
Differential I/O Connections and Header Connections
Differential Pair
Signal Name
FPGA Ball
FPGA Pin Name
Signal Direction
Header.Pin
“Receive” Header, J2 (Top Header)
RX_<0>
RXN_<0>
B4
IO_L31N_0
I/O
J2.6
RXP_<0>
A4
IO_L31P_0
I/O
J2.5
RX_<1>
RXN_<1>
A5
IO_L28N_0
I/O
J2.10
RXP_<1>
B6
IO_L28P_0
I/O
J2.9
RX_<2>
RXN_<2>
A6
IO_L26N_0
I/O
J2.14
RXP_<2>
A7
IO_L26P_0
I/O
J2.13
RX_<3>
RXN_<3>
A8
IO_L22N_0
I/O
J2.22
RXP_<3>
A9
IO_L22P_0
I/O
J2.21
RX_<4>
RXN_<4>
C10
IO_L21N_0
I/O
J2.26
RXP_<4>
A10
IO_L21P_0
I/O
J2.25
RX_CLK
RX_CLK_N
A11
IO_L18N_0
GLK7
I/O
J2.30
RX_CLK_P
A12
IO_L18P_0
GCLK8
I/O
J2.29
“Transmit” Header J15 (Bottom Header)
TX_<0>
TXN_<0>
AA3
IO_L03N_2
I/O
J1..6
TXP_<0>
AB2
IO_L03P_2
I/O
J1.5
TX_<1>
TXN_<1>
AA4
IO_L04N_2
I/O
J1.10
TXP_<1>
AB3
IO_L04P_2
I/O
J1.9
TX_<2>
TXN_<2>
AB6
IO_L08N_2
I/O
J1.14
TXP_<2>
AA6
IO_L08P_2
I/O
J1.13
TX_<3>
TXN_<3>
AB7
IO_L10N_2
I/O
J1.22
TXP_<3>
Y7
IO_L10P_2
I/O
J1.21
TX_<4>
TXN_<4>
AB8
IO_L12N_2
I/O
J1.26
TXP_<4>
AA8
IO_L12P_2
I/O
J1.25
TX_CLK
TX_CLK_N
AB10
IO_L15N_2
I/O
J1.30
TX_CLK_P
AA10
IO_L15P_2
I/O
J1.29