AR #16647 - 7.1i XST - "WARNING:NgdBuild:457 - logical net 'myin_ibuf' has an active driver and a pullup"
7.1i XST - "WARNING:NgdBuild:457 - logical net 'myin_ibuf' has an active driver and a pullup"
| AR# | 16647 |
| Topic | SW-XST |
| Last Modified | 2009-01-07 00:00:00.0 |
| Status | Archive |
Description
Keywords: instantiate, VHDL, Verilog, pull-up
Urgency: Standard
General Description:
When pull-ups are instantiated into sub blocks and the hierarchy of my entire design is preserved, XST does not recognize the pull-ups at the global I/O bufferization process. This results in XST placing IBUFs before the pull-ups and the following warning occurs:
"WARNING:NgdBuild:457 - logical net 'net_name' has an active driver and a pullup."
As a result, the final implementation does not have the desired pull-up in the I/O pad.
Solution
You can work around this issue by making these pull-ups visible in the top level using one of the following methods:- Manually move pull-ups to the top level.
- Put keep_hierarchy=no on the block where the pull-ups are instantiated or set the keep_hierarchy=no.
NOTE: The keep_hierarchy global setting is an advanced option. To enable advanced options, refer to (Xilinx Solution 11088). By default, the keep_hierarchy is set to "no". To change the keep_hierarchy setting, follow these steps:
1. Right-click the "Synthesize" process.
2. Select "Properties..."
3. Select the "Synthesis Options" tab.
4. Deselect the Keep Hierarchy setting.