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electronic:ttl:start [2021/03/31 15:42] – [Overview] tonyelectronic:ttl:start [2026/09/26 20:58] (current) – tony
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 ===== Overview ===== ===== Overview =====
 Early microcomputers used CRT displays driven by TTL level control signals. There was monochrome TTL, monochrome Hercules TTL (different sync frequencies, with bit mapped graphics), and CGA/EGA compatible TTL. Early microcomputers used CRT displays driven by TTL level control signals. There was monochrome TTL, monochrome Hercules TTL (different sync frequencies, with bit mapped graphics), and CGA/EGA compatible TTL.
 +
 +===== TTL from VGA Port =====
 +Driving TTL from VGA from a RaspberryPi 3 (( [[https://www.reddit.com/r/retrobattlestations/comments/5jslch/raspberry_pi_running_ibm5151_monitor_via_hdmivga/]])):
 +
 +Wire VGA green to the video input and let the monitor chop off the values on it's own (it's a TTL display).
 +
 +Wiring diagram:
 +
 +|HD15|6|->|DE9|1|
 +|HD15|2|->|DE9|7|
 +|HD15|13|->|DE9|8|
 +|HD15|14|->|DE9|9|
 +
 +Video settings from /boot/config.txt:
 +
 +|# hercules/ibm5155 crt|
 +|hdmi_ignore_edid=0xa5000080|
 +|hdmi_group=2|
 +|hdmi_mode=87|
 +|hdmi_timings=720 1 16 130 16 350 0 16 16 16 0 0 0 50 0 16257000 0|
 +----
 +Others say:
 +http://old.pinouts.ru/Video/MDA_pinout.shtml combine RGB signals on the VGA connector together with, say, 330 ohm resistors. Connect H-sync on VGA to H-sync on MDA, same for V-sync, and connect the ground and the MDA intensity line to ground.
 +
 +VGA outputs are supposed to be 0.7v (probably higher on some implementations without a proper 75 ohm load though) and MDA is TTL logic level, where >2.4V is considered a high, <.8 is considered a low, and in between is undefined....
  
 ===== Hardware description ===== ===== Hardware description =====
 +\\
  
 ====== References and Additional Resources ====== ====== References and Additional Resources ======
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   * [[https://forum.arduino.cc/index.php?topic=423321.0]]   * [[https://forum.arduino.cc/index.php?topic=423321.0]]
   * [[http://forums.nesdev.com/viewtopic.php?p=77213]]   * [[http://forums.nesdev.com/viewtopic.php?p=77213]]
 +  * [[https://www.reddit.com/r/retrobattlestations/comments/5jslch/raspberry_pi_running_ibm5151_monitor_via_hdmivga/]]
 +  * [[https://old.pinouts.ru/Video/MDA_pinout.shtml]]
  
  

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electronic/ttl/start.1617205350.txt.gz · Last modified: 2021/03/31 15:42 by tony
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