Lab 4 Tips


Lab 4 is an introduction to the equipment found in the CS150 lab. The most 
important tool that you will be useful to understand and use is the oscilliscope.
 It will be your debugging tool for future labs and projects. A good 
understanding of this tool and how to use to analyze digital signals and measure 
delays will be very useful. So take good care to understanding this tool.

KEY: Become familiar with the digital probes of the oscilliscope. Learn to read 
digital signals, learn to trigger on certain patterns, and learn to freeze and 
measure delays and bits from the digital waveforms.



Loading the BIT files:

- You do not need the XILINX Project Manager software to load a bit file to the 
XILINX board.

- Open the Debugger loader by going to the Start Menu --> Xilinx Foundation... 
--> Accessories --> Hardware Debugger.

- This is rather counter-intuitive; when you load a BIT-file onto the XILINX 
board, do NOT open a project. Rather, create a NEW PROJECT and load the bit file 
from there.

- Again, you will need to map the CS150 folder to a drive under 
\\fileservice\cs150 and copy the LAB4 folder to your local directory or desktop.


Reading the bits from the ROM:

- Reading the bits on the oscilliscope can be a little tricky.

- On the screen of the oscilliscope, TIME increases from left to right. Therefore
 the first bit you receive will be on the left side of the screen and the last 
bit you receive will be on the right side.

- The bits that output from the ROM are sent out from least significant bit first
 (bit 0 first) to the most significant bit last (bit 15 last). This means that 
reading the bits from left to right, you will have to reverse the bits so that 
they are in correct bit-wise order.

- Also since it will be easier to show us TAs the number in hexidecimal form, it 
would be easiest to "read" the bits in groups of four. Use the CURSOR function 
and set one cursor at the beginning of the four-bit group and the second cursor 
at the end. Lock the two cursors together and use them to mark off each four bits.


Revision to Lab:

Several things that will make your life easier for the lab, follow the below 
instruction:

- In the part of the lab where you are required to use the analog probes in 
measuring the signal coming out of the ROM, replace the analog probes with the 
digital pin-out probes. They are the small spaghetti-like probes that are already
 attached to the oscilliscope. 

- Another revision is the last part of the lab. Rather than triggering on the 
counter at 1110, and then step the clock to 1111 use a different method. 

- Using the PATTERN option on the oscilliscope, set the combination of bits, 
depending on which probe you used, to the 2nd through 4th bit being set to 
H, H, H and the 1st bit being set at L-->H (which on the oscilliscope is 
represented by a small arrow going low to high). 

- Also rather than running the scope on RUN mode, set it to SINGLE mode, which 
will trigger on the first pattern and freeze the waveform.

- Let the oscilliscope trigger on that combo and you will be able to observe the 
final output without having to step the clock. You just have to start it and the 
correct waveform will be captured.