Intel® Quartus® Prime Standard Edition User Guide: PCB Design Tools

ID 683619
Date 9/24/2018
Document Table of Contents Constant Definition

The constant definition block of the simulation file instantiates the voltage sources that controls the configuration modes of the I/O buffer.

Constant Definition Block

* Constant Definition

voeb       oeb       0     vc  * Set to 0 to enable buffer output
vopdrain   opdrain   0     0   * Set to vc to enable open drain 
vrambh     rambh     0     0   * Set to vc to enable bus hold
vrpullup   rpullup   0     0   * Set to vc to enable weak pullup
vpcdp5     rpcdp5    0     rp5 * Set the IO standard
vpcdp4     rpcdp4    0     rp4
vpcdp3     rpcdp3    0     rp3
vpcdp2     rpcdp2    0     rp2
vpcdp1     rpcdp1    0     rp1
vpcdp0     rpcdp0    0     rp0
vpcdn4     rpcdn4    0     rn4
vpcdn3     rpcdn3    0     rn3
vpcdn2     rpcdn2    0     rn2
vpcdn1     rpcdn1    0     rn1
vpcdn0     rpcdn0    0     rn0
vdin din       0     0


  • Voltage source voeb controls the output enable of the buffer and is set to disabled for inputs.
  • vopdrain controls the open drain mode for the I/O.
  • vrambh controls the bus hold circuitry in the I/O.
  • vrpullup controls the weak pullup.
  • The next 11 voltages sources control the I/O standard of the buffer and are configured through a later library call.
  • vdin is not used on input pins because it is the data pin for the output buffer.