AT Blaster

The intent of this page is to provide some information on the use & programming of the Cypress CY7C68300A IDE to USB 2.0 interface chip.


Refer to the schematics and to the Cypress website for the datasheet, how to wire the part up, and so forth. The important thing is that the part will not function as a mass-storage device until its serial eeprom has been programmed. If the serial eeprom is blank the part will show up in Windows as an unknown USB device.  The file to program into the serial eeprom is below; do a right-click and then “save-as” or similar to save it to your harddisk.


EEPROM Programming with ATBlaster

The 24LC02 serial eeprom is programmed using the ATBlaster software from Cypress. This software is contained within the CY4615B design kit, downloadable off the Cypress website. To find this kit, go to, type “CY4615B” into the search field, top right, then select the reference design kit from the search results. Towards the bottom of the 4615B reference design kit page is a link to download the software files.

Installation of the software should be done with some forethought. There are two main considerations:

  1. The ATBlaster software installs a custom USB driver in Windows. This custom driver will prevent that copy of Windows from recognising your 7C68300A board as being a mass-storage device, unless you subsequently remove the driver (which is not trivial).
  2. The ATBlaster software does not work great under WinXP (at the time of writing – this may be improved by now.)

For these reasons I highly recommend installing ATBlaster either on a separate “test” Windows machine, or on (for example) a Win98 installation on a separate partition on your main PC. In my case I did the latter; I installed Win98 on a separate partition and I boot that Win98 whenever I need to run ATBlaster.

The machine you install ATBlaster on needs a USB port, but USB 1.1 is fine. USB 2.0 is not required to do the programming.

Do not install ATBlaster on WinXP; it’s a pain. Nor on Win95 or Windows 3.1, as those OS’s don’t support USB ports. Windows 98, ME, NT, and 2000 are possible OS’s. If you have the option, pick Win98, simply because I know from my experience, and the experience of others, that it works.

If you install ATBlaster on your main PC, ignoring my advice to install it on a separate “test” copy of Windows, please remember that you will need to uninstall the ATBlaster USB driver before your PC will recognise the mass-storage device.

With ATBlaster installed, you can now plug in your USB board containing the 7C68300A chip and serial eeprom, and run the software. It’s pretty simple to use; just play with it. My USB2 page contains the serial eeprom file I program into my eeproms. Once you’ve programmed the eeprom I highly recommend you do a read back from the eeprom to ensure you really did program it.

Uninstalling the USB Driver

I have never done this; the following email was forwarded to me by a person who wanted to do this in Windows 2000 and asked Cypress technical support how. I have copied it here for your information. If you have any other questions on doing this please don’t email me; I’ve never done it. Instead, ask Cypress and then send me the answer, I will post it here for everyone to see.

In addition, this Cypress application note describes how to change the mass-storage class driver in Windows. This document should answer most questions.


Thank you for using the Cypress On-Line ConnectionCenter™. In reference to your questions:

Q1: I did a board using CY7C68300A, this board has only it and a connector to a harddrive and the 24c02 eeprom. I connect the board to a linux system and I can see the hard drive as a mass storage device, but into windows 2000 I see the board as a Cypress manufacturing driver at2, what am I doing wrong???

A1: It looks as though you (or someone) has used that computer also for programming the EEPROM for the CY7C68300 AT2. What you need to do is some registry clean up, since your device has been enumerated on the OS, the OS will register the fact that it has been setup previously and that it used the cymfg.sys. To clean up the registry:
Registry Cleanup

Windows 2000
Select Start and then Run in the start bar.
When the Run dialog box appears type in regedt32 and press OK.
Expand CurrentControlSet
Expand Enum
Expand USB
Now you should see all of the VID/PIDs that have been enumerated on that machine. If you expand your VID/PID you will see every device that has been enumerated with that VID/PID. Since each device should have a different serial number you should see a new folder for each device. It is probably easiest to delete your VID/PID folder altogether but you can choose to delete the individual devices if you want to be more specific. You will need to be administrator to do this and will have to go to the security menu item to change the permissions. When done close out the registry editor and reboot your machine.

You also might want to check if you have the cymfg.inf file and remove your VID/PID for your operational device from that file.

The Cypress applications note titled “How to Switch to a Different Mass Storage Driver in a Windows-Based Operating System” should also help.

It is our goal at Cypress to provide complete customer satisfaction. If you would like to add any additional comments or inquiries, please do so at this time. If you believe we have responded appropriately to your concerns, please close this case. To close this case, please select the Close radio button located in the upper right-hand corner of the case screen and then select Submit.

Cypress Applications Support


Note added March 2005. Over the last few months Cypress has completely changed their website. Many useful files that were present on the old website can no longer be found. If you need the ATBlaster files, try emailing me.