optionsdoc.htm

用VHDL编写的串口异步通信的例子

 Gate is a power saving property that can be used in CoolRunner-II designs. 
 <!--kadov_tag{{<spaces>}}-->&nbsp;<!--kadov_tag{{</spaces>}}-->This option 
 allows you to turn Data Gate off in case you want the fitter to ignore 
 data gate.</p></li>
	
	<li class=kadov-p><p class="whs29"><span 
 style="font-weight: bold;"><B>Tristate Outputs Termination Node</B></span> -- 
 The Tristate Output Termination Mode globally sets all tristate outputs 
 to the specified termination mode. By default, this field is set to Pullup.. 
 <!--kadov_tag{{<spaces>}}-->&nbsp;<!--kadov_tag{{</spaces>}}-->The options 
 are Pullup, Keeper and Float.</p></li>
	
	<li class=kadov-p><p class="whs30"><span 
 style="font-weight: bold;"><B>Create Programmable Ground Pins on Unused I/O</B></span> 
 -- The Create Programmable GND Pins on Unused I/O property controls the 
 option to indicate that you want all unused I/O pads to be configured 
 as ground pins. This can reduce ground bounce. By default, this option 
 is set to ground. <!--kadov_tag{{<spaces>}}-->&nbsp;<!--kadov_tag{{</spaces>}}-->The 
 options are Ground, Pullup, Keeper and Float.</p></li>
	
	<li class=kadov-p>
	<p class="whs31"><span style="font-weight: bold;"><B>Default 
 Output Voltage Standard</B></span> -- set a default voltage standard for CoolRunner-II 
 device pins.</p>
	
	<p class="whs32">IOSTANDARD 
 names supported by CoolRunner-II are:</p>
	
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	<col class="whs35">
	<col class="whs36">
	<col class="whs37">
	
	<tr valign=top>
	<td width="20.209%" class="whs38">
	<p class="whs39">I/O Standard</td>
	<td width="16.192%" class="whs40">
	<p align="center" class="whs41">VCC<span style="vertical-align: Sub;">IO</span></td>
	<td width="22.217%" class="whs42">
	<p align="center" class="whs43">Input V<span style="vertical-align: Sub;">REF</span></td>
	<td width="41.383%" class="whs44">
	<p align="center" class="whs45">Board Termination Voltage (V<span style="vertical-align: Sub;">TT</span>)</td></tr>
	
	<tr valign=top>
	<td width="20.209%" class="whs46">
	<p class="whs47">LVTTL </td>
	<td width="16.192%" class="whs48">
	<p align="center" class="whs49">3.3V</td>
	<td width="22.217%" class="whs50">
	<p align="center" class="whs51">N/A</td>
	<td width="41.383%" class="whs52">
	<p align="center" class="whs53">N/A</td></tr>
	
	<tr valign=top>
	<td width="20.209%" class="whs54">
	<p class="whs55">LVCMOS33</td>
	<td width="16.192%" class="whs56">
	<p align="center" class="whs57">3.3V</td>
	<td width="22.217%" class="whs58">
	<p align="center" class="whs59">N/A</td>
	<td width="41.383%" class="whs60">
	<p align="center" class="whs61">N/A</td></tr>
	
	<tr valign=top>
	<td width="20.209%" class="whs62">
	<p class="whs63">LVCMOS25</td>
	<td width="16.192%" class="whs64">
	<p align="center" class="whs65">2.5V</td>
	<td width="22.217%" class="whs66">
	<p align="center" class="whs67">N/A</td>
	<td width="41.383%" class="whs68">
	<p align="center" class="whs69">N/A</td></tr>
	
	<tr valign=top>
	<td width="20.209%" class="whs70">
	<p class="whs71">LVCMOS18</td>
	<td width="16.192%" class="whs72">
	<p align="center" class="whs73">1.8V</td>
	<td width="22.217%" class="whs74">
	<p align="center" class="whs75">N/A</td>
	<td width="41.383%" class="whs76">
	<p align="center" class="whs77">N/A</td></tr>
	
	<tr valign=top>
	<td width="20.209%" class="whs78">
	<p class="whs79">LVCMOS15</td>
	<td width="16.192%" class="whs80">
	<p align="center" class="whs81">1.5V</td>
	<td width="22.217%" class="whs82">
	<p align="center" class="whs83">N/A</td>
	<td width="41.383%" class="whs84">
	<p align="center" class="whs85">N/A</td></tr>
	
	<tr valign=top>
	<td width="20.209%" class="whs86">
	<p class="whs87">HSTL_I</td>
	<td width="16.192%" class="whs88">
	<p align="center" class="whs89">1.5V</td>
	<td width="22.217%" class="whs90">
	<p align="center" class="whs91">0.75V</td>
	<td width="41.383%" class="whs92">
	<p align="center" class="whs93">0.75V</td></tr>
	
	<tr valign=top>
	<td width="20.209%" class="whs94">
	<p class="whs95">SSTL2_I</td>
	<td width="16.192%" class="whs96">
	<p align="center" class="whs97">2.5V</td>
	<td width="22.217%" class="whs98">
	<p align="center" class="whs99">1.25V</td>
	<td width="41.383%" class="whs100">
	<p align="center" class="whs101">1.25V</td></tr>
	
	<tr valign=top>
	<td width="20.209%" class="whs102">
	<p class="whs103">SSTL3_I</td>
	<td width="16.192%" class="whs104">
	<p align="center" class="whs105">3.3V</td>
	<td width="22.217%" class="whs106">
	<p align="center" class="whs107">1.5V</td>
	<td width="41.383%" class="whs108">
	<p align="center" class="whs109">1.5V</td></tr>
	</table>
	
	<p class="whs110">The software 
 automatically groups outputs with similar IOSTANDARD settings into the 
 same bank when no location constraints are specified. </p>
	</li>
</ul>

<h2 class="whs111"><a name="XC9500/XL/XV Advanced Options"></a>XC9500/XL/XV 
 Advanced Options</h2>

<p class="whs112">The following 
 options are found under the Advanced tab for XC9500/XL/XV. <!--kadov_tag{{<spaces>}}-->&nbsp;<!--kadov_tag{{</spaces>}}-->Note 
 that additional options for XC9500 only are also described below.</p>

<ul type="disc" class="whs113">
	
	<li class=kadov-h4><h4 class="whs114">Use 
 Global Clock(s) -- <span style="font-weight: normal;">Select this option 
 to allow the fitter to assign input pins used as clocks to dedicated global 
 clock (GCK) pins of the device. If this option is disabled, only pins 
 identified with the BUFG=CLK property in the design (or UCF file) will 
 be assigned to GCK device pins. By default, this option is on.</span> 
 </h4></li>
	
	<li class=kadov-p><p class="whs115"><span 
 style="font-weight: bold;"><B>Use Global Output Enable(s)</B></span> -- Select 
 this option to allow the fitter to assign input pins used as output enable 
 control to dedicated global OE (GTS) pins of the device. If this option 
 is disabled, only pins identified with the BUFG=OE property in the design 
 (or UCF file) will be assigned to GTS device pins. By default, this option 
 is on. </p></li>
	
	<li class=kadov-p><p class="whs116"><span 
 style="font-weight: bold;"><B>Use Global Set/Reset</B></span> -- Select this 
 option to allow the fitter to assign input pins used as register asynchronous 
 reset or preset control to the dedicated global set/reset (GSR) pin of 
 the device. If this option is disabled, only a pin identified with the 
 BUFG=SR property in the design (or UCF file) will be assigned to the GSR 
 device pin. By default, this option is on.</p></li>
	
	<li class=kadov-p><p class="whs117"><span 
 style="font-weight: bold;"><B>Create Programmable Ground Pins on Unused I/O</B></span> 
 -- Select this option to indicate that you want all unused I/O pads to 
 be configured as ground pins. This can reduce ground bounce. By default, 
 this option is off.</p></li>
	
	<li class=kadov-p><p class="whs118"><span 
 style="font-weight: bold;"><B>Macrocell Power Setting</B></span> -- Use this 
 option to control device power consumption. Select Low or Standard to 
 set the default power mode for the macrocells used to implement the design. 
 Select Timing Driven to automatically reduce power on paths covered by 
 timing specifications that can meet speed requirements while operating 
 in low power. The default is Standard, which results in highest speed.</p></li>
</ul>

<p class="whs119">Note: Any explicit power control (PWR_MODE) 
 properties in the design or constraints file take precedence over this 
 Macrocell Power Setting. </p>

<ul type="disc" class="whs120">
	
	<li class=kadov-p><p class="whs121"><span 
 style="font-weight: bold;"><B>Enable FASTConnect/UIM Optimization (XC9500 
 only)</B></span> -- Enables optimization of the FASTConnect/UIM for XC9500 
 devices.</p></li>
	
	<li class=kadov-h4><h4 class="whs122">Use 
 Local Feedback (XC9500 only)</h4></li>
</ul>

<p class="whs123">Select this option to enable the software 
 to use local macrocell feedback whenever possible. The local feedback 
 path, running from each macrocell output to an input of the same function 
 block, has shorter propagation delay than the global feedback path. The 
 fitter always tries to use local macrocell feedback (if possible) to satisfy 
 timing constraints. This option allows the fitter to use local feedback 
 to generally improve timing on remaining paths. Using local feedback can 
 speed up your design but could also make it difficult to maintain the 
 same timing after a design change. By default, this option is on.</p>


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<p class="whs124"><b><span style="font-weight: bold;"><B>Note: 
 </B></span></b>To force the fitter to use local feedback, manually map both 
 the source and load functions into the same function block using the property 
 <span style="font-weight: bold;"><B><b>LOC=FB</b></B></span><span style="font-style: italic;"><I><i>nn</i></I></span>, 
 then apply a timespec across the path.&nbsp;</p>


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<p class="whs125"><span><FONT SIZE=2 style="font-size:10pt;"><b style="font-weight: bold;">Note: 
 </b></FONT></span>The XC9536 device does not have local feedback.</p>


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<ul type="disc" class="whs126">
	
	<li class=kadov-h4><h4 class="whs127">Use 
 Pin Feedback (XC9500 only)</h4></li>
</ul>

<p class="whs128">Select this option to enable the software 
 to use I/O pin feedback whenever possible. The pin feedback path has slightly 
 shorter propagation delay than the global feedback path. If this option 
 is enabled, the software uses the pin feedback path instead of the global 
 feedback path for macrocell signals that do not drive 3-state outputs 
 or slew-rate-limited outputs, and where the associated I/O pin is not 
 used as input-only. By default, this option is on.</p>

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