PmWiki | Emulator / Panel

Class: Panel8, PanelLogic

Console emulator

Console of my PDP

The panel in my emulator was implemented purely in Java Swing components. You may see that the similarity to the real panel is rather good.

All buttons and lamps work like on a real PDP8. The switch register has a little extra feature that you should find out by yourself.

Preloaded in the pseudo-memory are:

What	Start address	Comments
ASCII display	0200	Displays all 7 bit characters continuously
Real time counter	0400	Real seconds in MQ if PC is fast enough
Echo routine	0600	Echoes TTY reader to output

Panel menu

If the emulator is in a halted state, the following bootstraps can be executed from the context-menus on the panel (See picture at right).

Also available is an option to regulate the speed of my emulator: it can either run at PDP8 speed (based on the basic 1.2 microsecond cycle time) or run at the maximum possible speed of the platform it is running on. The speed can be checked by executing he real time counter, mentioned before. To allow a better overview of the various registers I have added an option that provides a display similar to the PDP8/I. Lastly a check box allows switching off the time share feature.

What	Start address	Comments
SI4043 bootstrap	0000	Boots SI4043 on unit 0
SI4043 bootstrap	0000	Boots SI4043 on unit 1
TD8E bootstrap	7300	Boots TD8E on unit 0
Binary loader	7700	Low speed for TTY reader
Binary loader	7700	High speed for PTR reader
RIM loader	7756	Low speed for TTY reader
RIM loader	7756	High speed for PTR reader
Binary punch	7465	Start with AC clear, first halt: # blocks, each block: begin, end

The OS/8 date is stored in memory when starting the emulator. Most bootstraps preserve this location so that the date is set for the ensuing session. This date is naturally not the the current date, but reduced by the so-called 28 years setback. This preserves the weekdays and puts the date around 1985, which is convenient because most other historical files were created before this. The SI4043 bootstrap on unit 1 is to facilitate easy access to an extra disk. Units are just shifted up, so the real unit 0 is no longer accessible.

As already mentioned earlier, the Panel Logic runs with a thread that pauses every 20ms. It updates all lamps with their appropriate values. The switches are of two kinds. toggle or positional. Their values are transmitted to the corresponding values of the data object in BusRegMem.

Clicking the markers of the bus selector knob will position the knob at the desired position. The same applies to the power knob: setting it to off will simulate a power outage.