Altera MAX II - Manual (Page 18)

2–10 Development Kit Version 1.1.0 Altera Corporation
MAX II Development Kit Getting Started User Guide July 2005
Demo Designs
configured. Press S2 and the 000 changes to the number of times that
the MAX II device could have configured itself in that interval
(typical values should be between 300-600 for fast button pushers).
Test 2. Using a Scope to Measure Power-Up Times
1. Program the MAX II device with the InstantOnDemo.pof file that is
located in the /Examples/HW/Demos directory. (Refer to
“Programming the MAX II Device” on page 2–4 for details on how
to load POF files into the MAX II device.)
2. Attach scope probes to the four Active I/O test points located near
the prototyping area on the board.
3. Set the trigger on the scope to the channel connected to the V
CCINT
test point and trigger on the rising edge (LVTTL logic level).
4. Set the load on V
CCINT
to the desired amount by tuning the variable
resistor (potentiometer), labeled POT1.
5. Press S5 on the board to interrupt the power and observe the ramp
time of V
CCINT
via the provided test point. A sample screen is shown
below (see Figure 2–4 ).
Understanding the Results
The most detailed analysis of the power-up character of a MAX II device
comes from viewing probe points during the power-up cycle with a
digital oscilloscope. The development board has a variable core V
CC
rise
time control. This system uses POT1 to vary the MAX II core V
CC
rise time
from 80
μs to 150 ms. The on-board test points provide users with an easy
way to examine the ramp time of V
CCINT
and the resulting configuration
completion time. The ramp time of V
CCINT
can be varied with POT1, thus
allowing this circuit to match almost any system’s power-up rise time and
analyze how the MAX II device performs. To make power cycling even
easier, S5 will power cycle the MAX II V
CCINT
supply any time it is
pressed and released. The development board provides four useful probe
points:
■ V_INT = V
CCINT
(MAX II core voltage supply)
■ V_IO = V
CCIO
(MAX II I/O voltage supply)
■ GND = Board Ground plane
■ ACTIVE_IO = MAX II User I/O pin P12