Analyze protocol used for Futaba VFD display, 3 data pins
The controller inside this VFD tube is a Princeton PT6301. It features internal character memory (2x20), 2x20 icon memory, ASCII character ROM, user defined char RAM, drivers and multiplexers for the VFD. The interface is Data (LSB first), Clk, /CS and /Reset. Checkout the datasheet for the commandset.
The logic analyser trace matches the 12 char ASCII text shown on the display (eg NPO 1 HD). The string is preceded by several config/initialisation commands and followed by a 13th char to show the symbols for Dolby, email etc. That final char is one of the user defined chars that was defined as part of the config/initialisation to activate the correct segment (eg HD).
Note that your pinout diagram of the connector and the VFD tube above has some errors! Pins on the VFD (starting from the right side of your picture) should be: GND1, GND2, +35V DC (switched), 5V DC supply, OSC pin (RC network between 5V and GND), /RST, /CS, CLK, DAT, NC, NC
The 35V DC is generated on the PCB by a DC/DC converter. The 35V generator, the 5V supply and the filament supply are all enabled by Pin 3 on the external connector.