Instantiating Block RAM for Spartan 3E in VHDL without using COREGEN

Screw Coregen!

To use block RAMs directly, use RAMB primitives given in the Xilinx primitives handbook (here: http://www.xilinx.com/itp/xilinx9/books/docs/s3edl/s3edl.pdf.

The question not answered is how to insert them into the VHDL. Obviously they need to be called out as a component somehow.

The answer was in Xilinx's block ram application note (http://www.xilinx.com/support/documentation/application_notes/xapp463.pdf) but did not jump out on initial reading. It took this forum thread to point out that there are quite easy to use templates for intantiating primitives built right into ISE. In ISE, Edit => Language Templates => VHDL => Component Instantiation => Block RAM (it gets a little more complicated than that at the end, but the basic idea is there). This gives the component declaration, and most importantly the library call that contains the actual primitive, both as a bitmap and as a simulation library.

Most of the forum threads out there on this subject are entirely devoted to how to use the INIT label or whatever to specify the initial contents of the RAM. Not sure why this is so worried over.

Also, the Spartan3e RAM primitive declaration has a fancy "SSR" line which is separate from the gbinit; gbinit produces the contents specified in the INITs, SSR is some weird enable for putting a constant output on the data lines regardless of the value of the address lines.

5V to 3.3V signal translation

Results of recent search for available translation technologies:

1. CD4050 hex buffer can run from 3V to 18V but accepts higher than VDD level on the inputs. However, at 5V requires at least 3.5V for high level inputs. datasheet here

2. SN74LVCC3245A is the dual supply transciever commonly in use here. Comes in surface mount only. A side must be between 2.3 to 3.6V, B side must be between 3V to 5.5V. Control lines are on the A side. datasheet here

3. SN74LVC4245A is another dual supply transciever using LVC-only technology. Very similar to 74LVCC3245A except that on this one the A side is locked to 5V and the B side is 3.3V. DIR and OE are on side A. datasheet here

4. It turns out that there's a SN74LVCC4245A, which has the A port being the 5V side, but the range on the B port goes from 2.7V to 5.5V. This might be the one that I thought I was using when building the breadboard. datasheet here

5. The SN74LVC245A runs at 1.65V to 3.6V but can handle input levels up to 5.5V. datasheet here

6. Similarly, the SN74LVC244 runs at low voltages and can handle 5V inputs.

7. The 74HCT244, if run at 5V, requires only 2V as an input high level (consistent with TTL characteristics). datasheet here

8. The CD40109 is a low-to-high translator, but is only 4 to a package.

9. The CD4504 is also available in DIP, is a hex buffer that accepts extremely high input voltages above it's VDD, but it's not clear if it can be run at 3.3V

10. here's a fascinating forum thread where a bunch of other ideas, including the CD4504 are discussed.

McAffe CPU Usage Failure 12/23/2008

Some notes from the latest McAffe Fuckup on the XPS:

getting high CPU usage from mcscript_inuse.exe

After I killed it, a scan32.exe process went into high usage and I killed it also.

This thread on the McAffe forums mentions a hotfix that I haven't had time to try:

http://community.mcafee.com/showthread.php?t=219100&page=2

Here is more info on the hotfix. Later in the thread it is disowned as a fix for any problems:

http://forums.mcafeehelp.com/showthread.php?t=224094

Xilinx Starter Kit with Labview

National Instruments makes something called "Labview FPGA"

http://www.ni.com/fpga/

It costs at least $2.5K, more like $6K when you buy a "Full" Labview development system:

http://sine.ni.com/nips/cds/view/p/lang/en/nid/11834

Here is the full page from the NI site on using it with the Spartan 3e kit:

http://digital.ni.com/express.nsf/bycode/spartan3e

However, it seems to be for educational use only:
http://forums.ni.com/ni/board/message?board.id=170&message.id=290961

Here's a google search on the subject that brought up some YouTube hits:
http://www.google.com/search?hl=en&fkt=52109&fsdt=59828&q=Xilinx+Starter+kit+labview&aq=f&oq=&aqi=

Here's one of the YouTube videos
http://www.youtube.com/watch?v=-ulWxOyOfgM

USB drive not appearing in My Computer

The most common cause of all seems to be Adobe's #*%^ing software interfering with Windows, althought it is clear that other software makes the same mistake.

Resources:

http://www.eggheadcafe.com/software/aspnet/31563340/usb-flash-drive-not-appea.aspx

Describes a tortuous troubleshooting process that fingered Adobe Photoshop Album Starter Edition as the culprit. Indeed, when the problem occured today that is the program that pops up when I plug in my thumb drive.

http://www.techspot.com/vb/all/windows/t-6762-USB-Flash-Disk-not-appearing-in-Explorer.html

Describes the many alternate solutions, such as assigning a specific letter to the drive, rebooting, using a third-party version of explorer, etc, and the IE6 workaround.

***WORKAROUND*** is to use IE6 and type "My Computer" in the address bar. The reason why this works is that the fresh copy of IE is forced to check the partition tables (or something like that) and sees the new drive, whereas the Adobe software is blocking previously started copies from doing that, including the copy which is the desktop. THIS DOESN'T WORK FOR IE7 OR MOZILLA.

***Clensing the system**** The culprit process is apdproxy.exe. Deinstall it, or change the service startup to manual. If at all possible, remove as much crap from Adobe as can be removed and still leave PDF reader.

How to change the dpi on ppt slides saved as bmp or tiff

Using PowerPoint 2002:

Just increase the size of the slide. The DPI "magic number" seems to be locked into 72 dpi, but by increasing the size the saved image dimensions stay the same.

Found this and much info here: http://www.pptfaq.com/FAQ00052.htm

This says:

Exporting from PowerPoint to other file types

To export your PowerPoint slides to other file types (BMP, WMF, JPG, PNG, etc)
Open your presentation and choose Save As from the File menu.
In the Save As Type dropdown listbox, choose the file type you want to save.
Give the file a name and click OK.
PowerPoint asks whether you want to export just the current slide or your entire presentation. The question is worded a little oddly, so read the message carefully before clicking Yes or No.

Increase the resolution/quality of bitmaps from PowerPoint

The RnR PPTools Image Exporter add-in for PowerPoint gives you complete control over the resolution, destination, filenames and format of bitmaps you export from PowerPoint. It also gives you better quality images than you can get from PowerPoint in most cases.
Increase the resolution of your exported bitmaps without an add-in
When PowerPoint exports bitmap files, it uses the current Slide Page Size to determine the resolution (ie, number of pixels) in the files it makes. Here's the formula:

Image-width-In-Pixels = Slide-width-In-Inches x Magic-DPI-Number

What's the Magic-DPI-Number? That depends on the version of PowerPoint and (in PowerPoint 97 your video driver settings as well).

Here are a few rules of thumb in case you don't have access to the system you're supporting:

For PPT97, the Magic DPI Number is 96 if your video is set to Small Fonts, 120 if Large Fonts.
For PPT 2000 and 2002, the Magic DPI Number is 72.
For PPT 2003, the Magic DPI Number seems to wander from 80 to 96, perhaps depending on the service pack you have installed. But you can change that: See HOW TO: Change the Resolution of a PowerPoint Slide That You Export As a Picture
For PowerPoint 2007, the Magic Number is back to 96, 120 or whatever your Windows video display resolution is set to. But for PowerPoint 2007 with Service Pack 1, if you use the registry setting above, you'll get higher resoluton images, but they'll be corrupted. Don't bother.

That's the default -- how to change it?

To get higher resolution but bitmap exports, choose File, Page Setup (or File, Slide Setup) and increase the size of your Slide page. Keep the new size proportional to the old, please, or you'll distort your graphics, set text boxes to wandering randomly around the page and so on. We don't want that.

OR ... if you have PowerPoint 2003/2007 and have read the link above, you can fiddle with the registry each time you want to change resolutions. Not recommended for the faint of heart. Or anyone else.

The Microsoft knowledge base article on the registry mod is here: http://support.microsoft.com/kb/827745

Didn't try it as I didn't have PP 2003 or 2007