Front Panel and PCB

The front panel is the user's primary interaction with the computer aside from the data terminal. There are three push buttons on the front left side that the user can use to interact with the system, and 30 LEDs on the front to display various information to user. The front panel has two ribbon cables connected to it. One from the Backplane and one from the CPU6 Board.

Right click and "Save As..." or "Open Image in New Tab" for full resolution.

Switch Explanation

• R/F - This is a latching push button and R/F stands for (R)emovable / (F)ixed. This switch is technically Sense Switch #4 and is used by OpCode "0x1D BS4 - Branch if Sense Switch 4 is Set."
• OPSYS - This is a momentary push button and sets or resets Sense Switch #3. This is used by OpCode "0x1C BS3 - Branch if Sense Switch 3 is Set." This switch also sends a master reset signal down the backplane. As a result, I am currently unclear how this switch interacts with OpCode 0x1C.
• SELECT - This is a momentary push button and sets or resets Sense Switch #3. This is used by OpCode "0x1C BS3 - Branch if Sense Switch 3 is Set." This switch also sends a master reset signal down the backplane. As a result, I am currently unclear how this switch interacts with OpCode 0x1C.

LED Explanation

• ADDRESS - This displays the 16-bit memory address
• LVL - This displays the current interrupt level
• MAP - I am unclear as to what exactly this is displaying, however, we are fairly confident ABT means Abort
• FLMV - These display the status of the flags. F: Fault, L: Link, M: Minus, V: Value
• RUN/HALT - Simply shows whether the CPU is RUNning or HALTed

Additional Information

It is important to note that the Centurion system is an evolution of the ElDorado Electrodata EE200 minicomputer from the early '70s. While that machine featured a very different front panel, most of the functionality on that panel was relocated to a set of DIP switches on the CPU6 Board. Most notably, the four sense switches are still present, and in fact are used to force the bootstrap loader to jump to the DIAG board ROM data.

Schematic

This schematic was reverse engineered by tracing out each individual line on the board itself. We are fairly confident it is mostly correct, but there could be errors still present.

Note: The CL2 and CL3 LEDs are swapped from the wiring on the front panel, which gives incorrect indication of the interrupt level. We believe this may have been fixed by swapping the traces on the backplane on newer revisions. The counterfeit backplane which is a newer revision we think has these lines swapped to give a correct indication.

Desk System Front Panel

This front panel is quite a bit different as it only has three switches and three LEDs. It was intended for the Desk System and therefore needed to be much more compact. As a result, the CPU plugs directly into the backplane instead of the front panel. The front panel itself only has one ribbon cable connector, which also plugs directly into the backplane.

Right click and "Save As..." or "Open Image in New Tab" for full resolution.

PICTURES FORTHCOMING

Schematic

There is no schematic as yet for the desk system front panel.