AR# 4646


How to change XC4000XLA, XC4000XV, SpartanXL, and VIRTEX output drive current


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)


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


NET <netname> DRIVE=24;

Where the netname is the net between the OBUF and OPAD
AR# 4646
日期 10/19/2011
状态 Archive
Type 综合文章
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