IOB Switching Characteristic Guidelines
Testing of the switching parameters is modeled after testing methods specified by MIL-M-38510/605. All devices are 100%
functionally tested. Since many internal timing parameters cannot be measured directly, they are derived from benchmark timing
patterns. The following guidelines reflect worst-case values over the recommended operating conditions. For more detailed, more
precise, and more up-to-date timing information, use the values provided by the XACT timing calculator and used in the simulator.
Speed Grade
-4
-3
-2
Description
Symbol Min Max
Min Max Min Max Units
Input
Propagation Delays
Pad to I1, I2
TPID
TPLI
TPDLI
TIKRI
TIKLI
2.5
3.6
7.1
2.8
3.0
ns
ns
ns
ns
ns
Pad to I1, I2, via transparent latch (no delay)
Pad to I1, I2, via transparent latch (with delay)
Clock (IK) toI1, I2, (flip-flop)
Clock (IK) to I1, I2 (latch enable, active Low)
Set-up Time (Note 3)
Pad to Clock (IK), no delay
Pad to Clock (IK) with delay
TPICK
TPICKD
4.7
8.3
ns
ns
Hold Time (Note 3)
Pad to Clock (IK), no delay
Pad to Clock (IK) with delay
TIKPI
TIKPID
0
0
ns
ns
Output
Propagation Delays
Clock (OK) to Pad
same
Output (O) to Pad
same
3-state to Pad begin hi-Z (slew-rate independent)
3-state to Pad active and valid (fast)
(fast)
(slew rate limited)
(fast)
TOKPOF
TOKPOS
TOPF
4.6
11.2
5.8
12.4
4.2
ns
ns
ns
ns
ns
ns
ns
(slew-rate limited)
TOPS
TTSHZ
TTSONF
TTSONS
8.1
14.7
same
(slew -rate limited)
Set-up and Hold Times
Output (O) to clock (OK) set-up time
Output (O) to clock (OK) hold time
TOOK
TOKO
3.7
0
ns
ns
Clock
Clock High or Low time
TCH/TCL
4.0
ns
Global Set/Reset
Delay from GSR net through Q to I1, I2
Delay from GSR net to Pad
GSR width*
TRRI
TRPO
TMRW
7.2
ns
ns
ns
18.9
* Timing is based on the XC4005E. For other devices see XACT timing calculator.
** See preceding page
Notes: 1. Timing is measured at pin threshold, with 50 pF external capacitive loads (incl. test fixture). Slew rate limited output
rise/fall times are approximately two times longer than fast output rise/fall times. For the effect of capacitive loads on
ground bounce, see pages 8-8 through 8-10.
2. Voltage levels of unused (bonded and unbonded) pads must be valid logic levels. Each can be configured with the
internal pull-up or pull-down resistor or alternatively configured as a driven output or be driven from an external source.
3. Input pad setup times and hold times are specified with respect to the internal clock (IK). To calculate system setup time,
subtract clock delay (clock pad to IK) from the specified input pad setup time value, but do not subtract below zero.
Negative hold time means that the delay in the input data is adequate for the external system hold time to be zero,
provided the input clock uses the Global signal distribution from pad to IK.
3
XILINX [ XILINX, INC ]
