From within EPIC, you can add certain constraints to or delete certain constraints from the .pcf file. Constraints supported in EPIC are listed following.
| Constraint | Accessed Through |
|---|---|
| block asyncpaths | Main Window Attributes constraint dialog box |
| block comp | Component Attributes dialog box |
| block net | Net Attributes dialog box |
| block path | Path Attributes dialog box |
| define path | Created, edited, and removed with Add and Delete; viewed with Path Attributes dialog box |
| locate comp | Component Attributes dialog box |
| locate macro | Macro Attributes dialog box |
| lock comp | Component Attributes dialog box |
| lock macro | Macro Attributes dialog box |
| lock net | Net Attributes dialog box |
| lock placement | Main Window Attributes dialog box |
| lock routing | Main Window Attributes dialog box |
| maxdelay allnets | Main Window Attributes dialog box |
| maxdelay allpaths | Main Window Attributes dialog box |
| maxdelay net | Net Attributes dialog box |
| maxdelay path | Path Attributes dialog box |
| maxskew | Main Window Attributes dialog box |
| maxskew net | Net Attributes dialog box |
| offset comp | Component Attributes dialog box |
| penalize tilde | Main Window Attributes dialog box |
| period | Main Window Attributes dialog box |
| period net | Net Attributes dialog box |
| prioritize net | Net Attributes dialog box |
| prohibit site | Site Attributes dialog box |
In EPIC, net and component constraints are supported as attribute fields in the individual nets and components. Attributes are set with the Setattr command and are read with the Getattr command. All Boolean constraints (block, locate, lock, offset, and prohibit) have values of On or Off. Offset direction has a value of either In or Out. Offset order has a value of either Before or After. All other constraints have a numeric value and can also be set to Off to delete the constraint. All values are case-insensitive; “On” and “on” are both accepted. All constraints attributes can also be set with dialog boxes. Attributes and their corresponding constraints are listed following.
| Main Attributes | Constraint |
|---|---|
| penalize_tilde | penalize tilde |
| allnets_maxdelay | maxdelay allnets |
| allpaths_maxdelay | maxdelay allpaths |
| clknets_period | period |
| clknets_maxskew | maxskew |
| Component Attributes | Constraint |
|---|---|
| lock | lock comp |
| locate | locate comp |
| offset | offset comp |
| offset_comp1 | Argument to offset comp |
| offset_comp2 | Argument to offset comp |
| offset_order | Argument to offset comp |
| offset_direction | Argument to offset comp |
| offset_time | Argument to offset comp |
| block | block comp |
| Net Attributes | Constraint |
|---|---|
| lock | lock net |
| block | block net |
| prioritize | prioritize net |
| maxdelay | maxdelay net |
| maxskew | maxskew net |
| period | period net |
| Macro Attributes | Constraint |
|---|---|
| locate | locate macro |
| lock | lock macro |
| Path Attributes | Constraint |
|---|---|
| block | block path |
| maxdelay | maxdelay path |
| Site Attributes | Constraint |
|---|---|
| prohibit | prohibit site |
When you create a constraint within EPIC, the constraint is written into the PCF file in XILINX Constraint Language, whenever you save the design. When you use EPIC to delete a constraint and then save your design file, the line on which the constraint appears in the PCF file remains in the file and is automatically commented out.
If a net is locked, you cannot unroute any portion of the net: the entire net, a net segment, a pin, or a wire. To unroute the net, you must first unlock it. However, you can add pins or routing to a locked net.
The Lock Net [net_name] constraint in the PCF file results in EPIC displaying a net as locked. This lock can be removed within EPIC using the Net Constraints dialog box.
When EPIC shows a component as locked, one of the following constraints is set in the PCF file.
If a component is locked, you cannot unplace it, but you can unroute it. To unplace the component, you must first unlock it.
