7 Series FPGAs SelectIO Resources User Guide www.xilinx.com 113
UG471 (v1.5) May 15, 2015
ILOGIC Resources
• At time T
IDOCK
before Clock Event 1, the input signal becomes valid-high at the D
input of the input register and is reflected on the Q1 output of the input register at
time T
ICKQ
after Clock Event 1.
Clock Event 4
• At time T
ISRCK
before Clock Event 4, the SR signal (configured as synchronous reset in
this case) becomes valid-high resetting the input register and reflected at the Q1
output of the IOB at time T
ICKQ
after Clock Event 4.
ILOGIC Timing Characteristics, DDR
Figure 2-10 illustrates the ILOGIC in IDDR mode timing characteristics. When IDELAY is
used, T
IDOCK
is replaced by T
IDOCKD
. The example shown uses IDDR in
OPPOSITE_EDGE mode. For other modes, add the appropriate latencies as shown in
Figure 2-7, page 111.
Clock Event 1
• At time T
ICE1CK
before Clock Event 1, the input clock enable signal becomes
valid-high at the CE1 input of both of the DDR input registers, enabling them for
incoming data. Since the CE1 and D signals are common to both DDR registers, care
must be taken to toggle these signals between the rising edges and falling edges of
CLK as well as meeting the register setup-time relative to both edges.
• At time T
IDOCK
before Clock Event 1 (rising edge of CLK), the input signal becomes
valid-high at the D input of both registers and is reflected on the Q1 output of
input-register 1 at time T
ICKQ
after Clock Event 1.
Clock Event 4
• At time T
IDOCK
before Clock Event 4 (falling edge of CLK), the input signal becomes
valid-low at the D input of both registers and is reflected on the Q2 output of
input-register 2 at time T
ICKQ
after Clock Event 4 (no change in this case).
X-Ref Target - Figure 2-10
Figure 2-10: ILOGIC in IDDR Mode Timing Characteristics
(OPPOSITE_EDGE Mode)
1234567891011
T
IDOCK
T
ICE1CK
T
ISRCK
T
ICKQ
T
ICKQ
T
ICKQ
T
IDOCK
CLK
D
CE1
SR
(Reset)
Q1
Q2
T
ICKQ
UG471_c2_08_090810
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