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SRAM overview (with text-to-speech explanations)

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Circuit Description

The applet on this webpage demonstrates the structure of a typical static random-access memory (or SRAM for short). The animation sequence relies on the FreeTTS text-to-speech synthesizer for synchronized audio explanation. Just sit back, watch the animation, and listen to the explanations.

Please wait until the animation sequence has stopped (about 5 minutes), before exploring the circuit interactively via the input switches. Otherwise, click here. to open the standard applet without the animation and text-to-speech output.


If the simulation and animation works when running the applet, but you can't hear the speech output, you have probably not yet changed the security settings of your browser's Java virtual machine. The speech synthesis in FreeTTS relies on a few operations (audio output, but also property accesses etc.) that are forbidden for untrusted applets. Therefore, to really run this applet with speech-output enabled, you might have to edit your Java security configuration file. The easiest way is to use our Java Policy Editor, which helps you to edit the security settings.

If audio output still does not work on your system, please also check the following:

  • check that audio functions are enabled by your operating system.
  • check volume controls and speaker/headphone cables.
  • on Linux, stop all other programs that play audio (e.g. mp3 playback), then restart the Hades application or your browser (Hades applet). On many Linux systems, several incompatbile drivers (e.g. alsa/oss/artsd) are installed, and a running application will often access the sound device directly instead of accessing it via a mixer device. In such cases, other applications are denied access to the sound device.

If the applet doesn't work at all, and you are sure that Java is enabled in your browser, chances are that the applet simply did run out of memory. The default memory limit of 64 MBytes used for Java applets is a bit low when running Hades with text-to-speech output, because the speech dictionary, phoneme data, and audio sample buffer are all pretty large. Please check the applet usage page for information about increasing the memory limit; a value of 128 or 256 MBytes should be fine.

Print version | Run this demo in the Hades editor (via Java WebStart)
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Impressum http://tams.informatik.uni-hamburg.de/applets/hades/webdemos/00-intro/15-freetts/ram-overview.html