Libraries GuideChapter 8: Design Elements (OAND2 to OXOR2)
OFDI
Output D Flip-Flop (Asynchronous Preset)
XC3000
| XC4000E
| XC4000X
| XC5200
| XC9000
| Spartan
| SpartanXL
| Spartan2
| Virtex
|
|---|
N/A
| Macro
| Macro
| N/A
| N/A
| Macro
| Macro
| Macro
| Macro
|
OFDI is contained in an input/output block (IOB). The output (Q) of the D flip-flop is connected to an OPAD or an IOPAD. The data on the D input is loaded into the flip-flop during the Low-to-High clock (C) transition and appears at the output (Q).
The flip-flop is asynchronously preset, output High, when power is applied. FPGAs simulate power-on when global set/reset (GSR) is active. GSR defaults to active-High but can be inverted by adding an inverter in front of the GSR input of the STARTUP, STARTUP_SPARTAN2, or STARTUP_VIRTEX symbol.
Inputs
| Outputs
|
|---|
D
| C
| Q
|
|---|
D
| 
| d
|
d = state of referenced input one setup time prior to active clock transition
|
Figure 8.25 OFDI Implementation XC4000E, XC4000X, Spartan, SpartanXL