OK, now I pulled one of these off the front of a rack mount server (dell, I think) and it’s really a pretty old design. This display uses an 8-bit data bus for the character to display, and a 4 bit address bus to pick the digit to display it on. They also have a plethora of other features: individually flashing characters, blinking the display, brightness control, lamp test, and clear. First: the flashing characters. You can set a register for each character to set that character as either flashable or not, and set the characters that can flash to flashing or not. There is a second bit that can be set to blink all the characters at the same time. Next we have the lamp test function: this one sets the character to all on, and all the segments are on to see if any of them are out. The clear function is pretty obvious, the brightness control has three bits of control from off to full brightness. The code I have here on github is not a library (yet) mostly because I think I should use shift registers to minimize the pin count.
Siemens PLCD5583 arduino library/demo