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XC4036XLA Datasheet, PDF (7/14 Pages) Xilinx, Inc – XC4000XLA/XV Field Programmable Gate Arrays | |||
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XC4000XLA/XV Field Programmable Gate Arrays
I/O Signalling Standards
XLA and XV devices are compatible with TTL, LVTTL, PCI
3V, PCI 5V and LVCMOS signalling. The various standards
are illustrated in Table 6 and the signaling environment is
illustrated in Figure 4.
VCC Clamping
XLA/XV devices are fully 5V TTL I/O compatible if VCC
clamping is not enabled. The I/O pins can withstand input
voltages up to 7V. With VCC clamping enabled, the XLA/XV
devices will begin to clamp input voltages to one diode volt-
age drop above VCC. In both cases negative voltage is
clamped to one diode voltage drop below ground.
XLA/XV devices maintain LVTTL I/O compatibility when
VCC clamping is enabled, however full 5.0V TTL I/O com-
patibility is sacriï¬ced.
Overshoot and Undershoot
Ringing wave forms are allowed on XLA/XV inputs as long
as undershoot is limited to -2.0V and overshoot is limited to
+7.0V and current is limited to 100 mA for less than 10 ns.
If VCC clamping is enabled then overshoot will begin to be
clamped at VCC/VCCIO plus one diode voltage drop and
undershoot will be clamped to ground minus one diode volt-
age drop. In either case the current must be limited to 100
mA per pin for less than 10 ns.
Table 6: I/O Standards supported by XC4000XLA and XV FPGAs
Signaling
Standard
VCC
Clamping Output Drive
VIH_MAX
VIH MIN
VIL MAX
VOH MIN
VOL MAX
TTL
Not allowed 12/24 mA
5.5
2.0
0.8
2.4
0.4
LVTTL
OK
12/24 mA
3.6
2.0
0.8
2.4
0.4
PCI5V
Not allowed
24 mA
5.5
2.0
0.8
2.4
0.4
PCI3V
Required
LVCMOS 3V
OK
12 mA
12/24 mA
3.6
50% of
30% of
90% of
10% of
VCC/VCCIO VCC/VCCIO VCC/VCCIO VCC/VCCIO
6
3.6
50% of
30% of
90% of
10% of
VCC/VCCIO VCC/VCCIO VCC/VCCIO VCC/VCCIO
5.0 V Power
3.3 V Power
2.5 V Power
VCC (5 V)
5 Volt Device
TTL
LVTTL
VCCIO VCCINT
XC4000XV
LVTTL
VCC (3.3 V)
3.3 Volt Device
Ground
X7147
Figure 4: The Signalling Environment for XLA/XV FPGAS. For XLA devices the VCCIO and VCCINT supplies are
replaced by a single 3.3 Volt VCC supply, however, all indicated I/O signalling is still supported.
Express Conï¬guration Mode
Express conï¬guration mode is similar to Slave Serial con-
ï¬guration mode, except that data is processed one byte per
CCLK cycle instead of one bit per CCLK cycle. An external
source is used to drive CCLK, while byte-wide data is
loaded directly into the conï¬guration data shift registers
(Figure 5). A CCLK frequency of 10 MHz is equivalent to a
80 MHz serial rate, because eight bits of conï¬guration data
are loaded per CCLK cycle. Express mode does not sup-
port CRC error checking, but does support constant-ï¬eld
error checking. A length count is not used in Express mode.
Express mode must be speciï¬ed as an option to the BitGen
program, which generates the bitstream. The Express
mode bitstream is not compatible with the other conï¬gura-
tion modes. Express mode is selected by a <010> on the
mode pins (M2, M1, M0).
The ï¬rst byte of parallel conï¬guration data must be avail-
able at the D inputs of the FPGA a short setup time before
the second rising CCLK edge. Subsequent data bytes are
DS015 (v1.3) October 18, 1999 - Product Speciï¬cation
6-163
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