Altera Early SSN Estimator - Manual (Page 9)

Chapter 1: Early SSN Estimator 1–5
Setting up the Early SSN Estimator
© November 2009 Altera Corporation Early SSN Estimator User Guide for Altera Programmable Devices
Parameters Specific to the I/O Bank
Figure 1–4 shows the ESE parameters for a given bank.
■ Bank VCCIO—All pins in an I/O bank share a common VCCIO voltage. Sharing
the VCCIO voltage restricts the combinations of legal I/O standards that can be
present within an I/O bank. Selecting a VCCIO voltage automatically populates
the I/O standard drop-down box with the set of I/O standards that are supported
by the given VCCIO voltage.
■ I/O Standard—The calculator supports up to four different I/O standards in a
single bank. If the I/O standard you are interested in is not shown in the drop
down box, ensure that the bank VCCIO voltage has been set correctly.
■ Drive Strength—Altera devices support multiple drive strengths depending on
the I/O standard. This drop down menu allows you to select valid values.
■ Slew Rate—Altera programmable devices support the control of the output
slew-rate that you can configure to balance noise and performance. A faster slew
rate provides high-speed transitions for high-performance systems. A slow slew
rate helps reduce system noise, but adds a nominal delay to rising and falling
edges.
1
The slew rate control option is not available for all Altera programmable
devices. For example, Stratix II GX devices do not offer the slew rate option.
■ Number of Outputs or Bidirectional Pins—The ESE tool models simultaneously
switching outputs-induced SSN. Switching inputs are not modeled because the
ESE has no information on what device is driving an FPGA input. Enter the
number of outputs or bidirectional pins that correspond to your selected I/O
standard and drive strength.
■ V
IL (DC)
/V
IH (DC)
Thresholds—The ESE bases its margin estimates on the input
thresholds of the receiving device. By default, the V
IL (DC)
and V
IH (DC)
parameters
are automatically populated with their I/O standard-specific values when you
select an I/O standard. You can manually change the values to any threshold
values.
Figure 1–4. Parameters Specific to an I/O Bank