Published 31 Mar 2021

TTL Displays

\\ ===== 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. ======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 ===== ====== References and Additional Resources ====== * [[https://www.diericx.net/post/drive-cga-screen-with-arduino/]] * [[https://techblog.vsza.hu/posts/Arduino_vs._CGA_part_1_-_flag_PoC.html]] * [[https://forum.arduino.cc/index.php?topic=423321.0]] * [[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]]

If any referenced page no longer exists, try looking for its URL on http://archive.org.

 \\ ----
 [[:start|Home Page]]   [[:about|About this Site]]   [[:copyright|Copyright Questions]]   [[:contact|Contact Us]]
\\ \\