10/09/2018
I recently received an interesting question about sending a monochrome signal to a modern display using VGA.
I found this interesting, from < https://en.wikipedia.org/wiki/IBM_Monochrome_Display_Adapter > :
"Adapters exist to convert MDA into VGA for upgrading to LCD. Using a GBS-8219 with the video signal (to G) and the horizontal sync (to H/CS) and vertical sync (to V); set to a RGB(D), and Sync Separate(HV)."
I would have some reservations about feeding the TTL pixel signal directly into the green analog input, as the TTL signal is 0-5V and the analog video input is designed to operate at only 0-0.7V. However, by adding two resistors, you could divide the signal level by about 1/7. (If you want to get fancy, you could even adjust the color by connecting the red and/or blue analog inputs to the same or similar resistor dividers. Back in the day, I preferred running an amber monochrome display to the more-common green screens.)
Note that the BIT-C-128 Video DAC is not used for this application.
To convert the scan rates, I recommend using the Gonbes GBS-8220. It provides good performance at a good price, as long as you use with it a power adapter of good quality.
The Monochrome Display Adapter (MDA, also MDA card, Monochrome Display and Printer Adapter, MDPA) is IBM's standard video display card and computer display standard for the PC introduced in 1981. The MDA does not have any pixel-addressable graphics modes. It has only a single monochrome text mode (P...
