Answers Database
How to change XC4000XLA, XC4000XV, SpartanXL, and VIRTEX output drive current
Record #4646
Product Family: Documentation
Product Line: FPGA Core
Product Part: docs
Problem Title:
How to change XC4000XLA, XC4000XV, SpartanXL, and VIRTEX output drive current
Problem Description:
Urgency: Standard
General Description:
For the XC4000XLA, XC4000XV, and SpartanXL devices, you can
change the output drive current for each IOB to either High(24mA)
or Low(12mA).
For the Virtex devices, you can select the output drive strength(mA)
for the components that use the LVTTL interface standard.
The applicable elements are:
1. IOB output components (OBUF, OFD, etc.)
2. OBUF, OBUFT, IOBUF instances (with implied LVTTL standards)
Solution 1:
For the XC4000XLA, XC4000XV, and SpartanXL devices, the syntax is:
DRIVE = {12 | 24 }
For the Virtex devices, the syntax is:
DRIVE = {2 | 4 | 6 | 8 | 12 | 16 | 24 }
Note: Drive current can only be specified on the LVTTL I/O standard
This attribute can either be placed to a valid IOB output component
in a schematic or via a UCF/NCF file.
The syntax in a UCF/NCF file for example would be:
INST /top/my_design/obuf DRIVE = 24 ;
Where the instance name is the name of the OBUF
Or
NET <netname> DRIVE=24;
Where the netname is the net between the OBUF and OPAD
End of Record #4646 - Last Modified: 10/15/99 15:01 |
