Other Special Components

To complete the Calc design, add a STARTUP symbol to make the logic resetable. Also, adding a CONFIG symbol allows specifying the Xilinx part number on the schematic.

The STARTUP Block (Optional, Spartan/XL, XC4000E/EX, and XC5200 only)

The STARTUP block allows global control of different aspects of a design. In this example, STARTUP connects an external signal to the global set/reset net built into the XC4000 family and XC5200 architectures. This global net connects to all flip-flops in the device and sets or resets them asynchronously. (Set or reset is determined at the flip-flop level.) Using this built-in resource wastes no routing resources tying a system-wide reset signal to all flip-flops in the design. For more information on STARTUP, see the Xilinx Libraries Guide.

The STARTUP symbol here implements a system-wide reset signal called NOTGBLRESET. This signal is active-low; therefore, when NOTGBLRESET is low, the Calc circuitry resets.

1. In the Calc schematic, add the components, nets, and labels as shown in the “Adding the STARTUP Symbol” figure. IPAD resides in the xcepads library, and you can take IBUF, INV, and STARTUP from the Xilinx device library (xce4000e or other family). Alternatively, you can enter the command “add ibuf” to add the IBUF, and similar commands to add the STARTUP, INV, and IPAD.
   
   

   Figure 9.39 Adding the STARTUP Symbol

   You add an inverter to the signal path because the GSR pin on STARTUP is active-high. Also, because GSR connects implicitly to all reset logic throughout the device, GBLRESET connects only to the GSR pin on the STARTUP block.
   
   

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   NOTE

   If you target an XC5200 device, connect your chip-wide reset signal to the GR pin on the STARTUP module.

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2. Write the Calc design.
   
   

Adding the CONFIG Symbol (Optional)

The CONFIG symbol tells the place-and-route software how to process the design. In this example, the CONFIG symbol specifies the part number for this device.

To add the CONFIG symbol, complete the following steps.

1. From the Calc schematic, either enter the command “add config,” or select the part from the xce4000 library (or other Xilinx device library). Place this symbol in the lower-right hand corner of the Calc schematic.
   
   
2. Enter into Attribute mode and select the CONFIG symbol.
   
   
3. In the Attribute Form, click on Add, and enter the name as PART_TYPE, and the value as XC4003E-4-PC84 and click OK. This specifies an XC4003E device with -4 speed grade (approximately 4 nanoseconds delay through a CLB) in an 84-pin PLCC.
   
   The part value can take one of the following two formats.
   
   
   • [XC] part_number-speed-package
     
     
   • [XC] part_number-package-speed
     
     Therefore, you can use the following legal values for the part property.
     
     
   • XC4003E-4-PC84 (recommended)
     
     
   • XC4003E-PC84-4
     
     
   • 4003E-4-PC84
     
     
   • 4003E-PC84-4
     
     

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     NOTE

     If using a different device, type that device number into the Property Value field instead (for example, XC95216-10-PQ150).

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4. Move the property text to be within the CONFIG symbol as shown in the next illustration.
   
   

   Figure 9.40 Adding the CONFIG Symbol

5. Write the Calc schematic.