spartan3A 的VCCAUX如何设定?我的板上为3.3V

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 楼主| jonslover 发表于 2012-10-21 22:24 | 显示全部楼层 |阅读模式
spartan3A (XC3S400A)的VCCAUX手册上说是可以设定为2.5V或者3.3V的,我的板子上是3.3V的,手册说的默认是2.5V,板子能正常使用吗?如何才能将VCCAUX设定为3.3V
 楼主| jonslover 发表于 2012-10-21 23:04 | 显示全部楼层
This attribute affects the banking rules for I/O placement within the automated placer, as well as in the Pace pin assignments tool. It also affects the end-generated bitstream for the device.

If the CONFIG VCCAUX constraint is not set and a user chooses to change VCCAUX voltage to 3.3V instead of the default 2.5V, there could be problems with the threshold levels on the inputs. This should not cause any damage to the device, but the inputs to the device might not meet the higher threshold requirements, so there might be logic failures in your design.

UCF and NCF Syntax Example:

Placed on output or bi-directional port:

CONFIG VCCAUX="value";

Where value is 2.5 or 3.3

Example:

CONFIG VCCAUX=3.3;

IMPORTANT NOTE: For the Spartan-3AN devices, VCCAUX MUST be set to 3.3V. The software setting default is 3.3V, and this should not be changed.
 楼主| jonslover 发表于 2012-10-21 23:04 | 显示全部楼层
这是国外网站的解释,看来还是得约束
gaochy1126 发表于 2012-10-21 23:47 | 显示全部楼层
飘过学习了,这个还真是需要进一步的学习一下
jakfens 发表于 2012-10-22 10:32 | 显示全部楼层
GoldSunMonkey 发表于 2012-10-22 17:01 | 显示全部楼层
这是国外网站的解释,看来还是得约束
jonslover 发表于 2012-10-21 23:04
约束:CONFIG VCCAUX=3.3;
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