VT52 Special Graphics

I was upgrading the images of the VT100 Special Graphics character set used in my online transcripts of the manuals today and I wondered about the VT52 equivalents, which are not shown graphically in any of the manuals that I could find; only the descriptions exist.

However, Fritz Mueller dumped the VT52 character generator ROM some years ago, so I thought I’d take a quick look.

In short, the VT52 Special Graphics look like this:

This is a lazy interpretation of the ROM, using a very similar script to that which I use to process the VT100 glyphs, so I haven’t included the extra scan lines that appear between text lines on the VT52, which is either 2 or 3, depending on whether you’re running at 60 Hz or 50 Hz, respectively. I also haven’t checked the aspect ratio of the characters; the Maintenance Manual provides dimensions for the complete raster which I could use.

Two things strike me as odd about this picture:

1. The second glyph is marked as “reserved” in all the manuals I’ve seen, so I have no idea what “cd” is supposed to represent, and whether the same glyph is present in all models of the VT52, and

2. The VT52 Maintenance Manual claims that only 7 scanlines are retrieved from the character generator ROM, which is clearly incorrect, as there is a glyph containing a horizontal line for each of the 8 scanlines that appear on the display.