User manual DIGIDESIGN MH038

[. . . ] Universal Slave DriverTM User's Guide Version 3. 0 Digidesign Inc. 3401-A Hillview Avenue Palo Alto, CA 94304 tel: 415·842·7900 fax: 415·842·7999 Technical Support (USA): 415·842·6699 415·856·4275 Product Information: 800·333·2137(USA only) 415·842·6602 America On Line: Keyword: Digidesign Compuserve: Go Digidesign World Wide Web: http://www. digidesign. com Digidesign FTP Site: ftp. digidesign. com Universal Slave Driver Project Team: Jeff Bell, William Bembo, Jan Biles, Neal Breitbarth, Johann Bryant, Vicky Fontes, Mary Horner, Mark Kirchner, David Kwan, Sam LaMacchia, Mildred Low, Donna Mathis, Des Medeiros, Terri Merrell, Christopher Michael, Kevin Miller, Mike Newman, Demetri Patukas, Lupe Portugal, Rene Pulido, Ed Rios, Kevin Turner, Michael VanLandingham, and John Weitz. Universal Slave Driver Firmware and Setup Software: Sam LaMacchia Universal Slave Driver Hardware: Christopher Michael Universal Slave Driver Manufacturability: Johann Bryant Universal Slave Driver User's Guide: Brent Hurtig and David Kwan Illustrations: David Kwan Cover Design: Van Chuchom Product Management: Mike Newman Special Thanks to: Dave Clementson, Rob d'Amico, John Duesenberry, Dave Lebolt, Jim Jasmin, Jeff Mock, Mike Rockwell, Dana Ruzicka, Mike Cuddy, and the entire Hi-Thigh/Low-Jitter Digidesign chorus line. This manual is copyrighted ©1997 by Digidesign, a division of Avid Technology, Inc. Under copyright laws, this manual may not be duplicated in whole or in part without the written consent of Digidesign. [. . . ] However, they do contain enough information for the Universal Slave Driver to calculate positional information. Here's how this works: Bi-phase/Tach signals use two square waves to generate pulses that can function as a clock reference. The two square waves are 90° out-of-phase, in a pattern that resembles this: Square Wave A Square Wave B Note: Some brands of older 3/4" U-matic VTRs have time code address tracks which have a fixed offset of several frames when compared with the audio tracks (which exactly match the video in terms of time). This could cause problems when using your Universal Slave Driver's LTC/VITC auto-switching capabilities. You can verify proper synchronization between your time code and address tracks by comparing the Universal Slave Driver's time code reader numbers, when "looking" at the various tracks, to an on-screen "window burn, " on the video work print supplied by the post-production house. Alternatively, you can With a Bi-phase signal, the Universal Slave Driver can deduce the direction (forward or reverse) of the signal based upon which wave is read "high" relative to the other. For instance, with some film equipment, when the device is running forward, it will generate a Biphase signal where the "A" wave leads the "B" wave-- that is, where the A wave peaks before the B wave peaks. When the device is in reverse, the B wave will lead the A wave. 58 Universal Slave Driver User's Guide However, some film equipment works in the opposite manner, which is why the Universal Slave Driver's Input Signals option lets you make the appropriate selection (Fwd = A leads B, or Fwd = B leads A). The "A" signal is a square wave that provides clock information; the "B" signal is in a steady state (high or low) that indicates the direction. Unfortunately, not all Tach-generating equipment uses the B signal in the same way. Fortunately, the Universal Slave Driver's Input Signals options allows you to choose the appropriate method (Tach: Fwd = B is Low, or Tach: Fwd = B is High). Now you can understand how the Universal Slave Driver can use a Bi-phase/Tach signal to deduce the direction, and how it also uses the signal as a clock reference. However, in order to use the signal as a positional reference, the Universal Slave Driver also needs to know time code address of the starting frame of the first clock signal. Since the Bi-phase/Tach doesn't contain this information, we need to "tell" the Universal Slave Driver what the starting frame is. To select the starting frame for a Bi-phase/Tach signal: At this point, the Universal Slave Driver knows two vital things about the Bi-phase/Tach signal: its direction, and its starting frame. Given these two things, the Universal Slave Driver can interpolate and accurately calculate location, just as if the Bi-phase/ Tach signal were time code. To use Bi-phase/Tach as the Universal Slave Driver's positional reference: 3 1. Select Bi-phase/Tach under USD Setup's Positional Ref pop-up menu. Set the Input Signals option, as appropriate: Selecting Bi-phase/Tach input signals Occasionally, when you use Bi-phase/Tach as the positional reference, you'll also be using it as the clock reference, so be sure to follow all the appropriate steps as described earlier. Finally, ensure that the Bi-phase/Tach signal is routed to the Universal Slave Driver's Bi-phase/Tach/GPI/Pilot Tone connector, and is wired properly, as described in Appendix I. Generate 1. In the Generator/Bi-phase Preset section, type in the time code value of the starting frame, in hours:minutes:seconds:frames. (Use your mouse or the Tab key to toggle between the fields. ) In this mode, the Universal Slave Driver generates its own positional reference. This feature is detailed in the next section. Setting the Generator/Bi-phase Preset 2. When you have inputted the proper starting frame, click Set. Using the USD Setup Software (Remote Control) 59 Generating & Regenerating Time Code & Clock Information The Universal Slave Driver outputs time code and clock information in one of two modes: Read/Regeneration Mode and Generator Preset Mode. [. . . ] As a side-note, the "calibration" units are in 1/64th of a sample period. What this means is that the Universal Slave Driver can theoretically be calibrated to about 1/3 of a ppm. The unit will maintain calibration across a wide range in temperature. Long-term drift should be less than one ppm per year due to aging of the crystal. [. . . ]