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boards:ecb:scg:start [2019/05/14 09:40]
b1ackmai1er [Errata]
boards:ecb:scg:start [2019/05/14 09:52]
b1ackmai1er [Board Configuration]
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 ==== Board Construction ==== ==== Board Construction ====
  
-  * Earlier runs of this board required a patch for sound to work. This patch is documented in the [[https://retrobrewcomputers.org/n8vem-pbwiki-archive/0/35845334/48860720/33053543/index.htm|Legacy Wiki SCG Folder]]. 
   * Install **either**  Q3 **or**  P2, but not both. These are mutually exclusive options for the video amplifier circuit.   * Install **either**  Q3 **or**  P2, but not both. These are mutually exclusive options for the video amplifier circuit.
   * Crystal X2 **must**  be parallel resonant. Installation of a series resonant crystal will result in the video controller chip running at the wrong frequency and colours may not be displayed correctly.   * Crystal X2 **must**  be parallel resonant. Installation of a series resonant crystal will result in the video controller chip running at the wrong frequency and colours may not be displayed correctly.
   * The TMS9918 video controller is sensitive to CPU clock speeds. In general, I have found all software posted here to function well at 4MHz. Higher CPU speeds may or may not work. It is normal for the TMS9918 chip to run quite hot.   * The TMS9918 video controller is sensitive to CPU clock speeds. In general, I have found all software posted here to function well at 4MHz. Higher CPU speeds may or may not work. It is normal for the TMS9918 chip to run quite hot.
   * Joystick interface is digital. The up, down, left, right, and button switches should be normally open and shorted to ground to activate. An Atari 2600 joystick can be readily adapted. PC-style game controllers use potentiometers for up/down and left/right and are therefore **not**  appropriate.   * Joystick interface is digital. The up, down, left, right, and button switches should be normally open and shorted to ground to activate. An Atari 2600 joystick can be readily adapted. PC-style game controllers use potentiometers for up/down and left/right and are therefore **not**  appropriate.
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 </code> </code>
  
-You **must** short one (and only one) set of pins above. These pins allow scaling the audio chip oscillator input. The default configuration is no scaling with an osciallator frequency of 2.0MHz which is the maximum frequency allowed by the AT-3-8910 chip. Incorrect setting of the oscillator frequency will result in distorted sound output.+You **must** short one (and only one) set of pins above. These pins allow scaling the audio chip oscillator input. The default configuration is no scaling with an oscillator frequency of 2.0MHz which is the maximum frequency allowed by the AY-3-8910 chip. Incorrect setting of the oscillator frequency will result in distorted sound output.
  
 **JP1: TEST2 Enable** **JP1: TEST2 Enable**
  
-Shorting 1-2 will ground the TEST2 pin of the sound controller, otherwise the pin will be disconnected. You would normally leave this jumper open. The AY-3-8910 datasheet does not document the functionality of the test configuration.+Shorting 1-2 will ground the TEST2 pin of the sound controller, otherwise the pin will be disconnected. This jumper is normally left open as the AY-3-8910 datasheet does not document the functionality of the test configuration. However the YM2149 which is compatible with the AY-3-8910 uses Pin 26 to divide the master clock by two when pulled low.
  
 **J21: Interrupt Enable** **J21: Interrupt Enable**
boards/ecb/scg/start.txt · Last modified: 2021/11/29 08:45 by b1ackmai1er
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