This is a short tutorial for operating a bare PDP-8/E without any system
software using the KC8-EA Programmer’s Console. The console is used
to toggle in the RIM loader (a basic loader program for paper tapes). Then
the RIM loader is used to load the BIN loader (a more sophisticated paper
tape loader) from a paper tape. Then the BIN loader is used to load the
demo program from a paper tape into the core memory of the PDP-8/E.
Finally, the demo program will be executed.
This demonstrates the typical bootstrap process of a small PDP-8/E system
without mass storage (disks or DECtapes).
rotate demo program
by dropping the PAL source file “rotate.pal” (included in the
simulator distribution) onto the icon of the PAL-8 Assembler in the Finder.
The binary paper tape file “rotate.bin” appears in the Finder.
(When a file “rotate.rim” is generated, you must modify the
preferences of the PAL-8 Assembler.)
Configure the PDP-8/E Simulator to have (at least) an ASR 33 Console
Teletype and the KC8-EA Programmer’s Console attached and start the
simulator. Open the Help window for the KC8-EA Console and use Balloon
Help (or Help Tags to be enabled in the Help menu) in the KC8-EA Console
window to inform you about the features of the console. Close the Help and
the CPU window. Select “Reset” from the File menu.
- Toggle in the RIM loader:
Go to the KC8-EA Console, set the Switch Register (SR) to 7756 (a
switch down is a binary zero, switch up is a binary one) and depress
the Load Address key (LOAD ADDR). Note that the Memory Address display
now shows this address, the start address of the RIM loader. Set the
Indicator Selector switch to MD. Set SR to 6032 (KCC) and operate the
Deposit key (DEP). Note that the MD display now shows the value deposit
in memory and the Memory Address display is incremented by one enabling
you to load the next value into the next memory location. In the same
manner, setting SR to the desired value, then operating the DEP key,
toggle in successively the following opcodes of the RIM loader:
07756 6032 KCC / ALREADY TOGGLED IN
07757 6031 KSF
07760 5357 JMP .-1
07761 6036 KRB
07762 7106 CLL RTL
07763 7006 RTL
07764 7510 SPA
07765 5357 JMP 7757
07766 7006 RTL
07767 6031 KSF
07770 5367 JMP .-1
07771 6034 KRS
07772 7420 SNL
07773 3776 DCA I 7776
07774 3376 DCA 7776
07775 5356 JMP 7756
07776 0000 AND 0
07777 5301 JMP 7701
Now check if you have toggled in the RIM loader correctly:
Set SR to 7756 and press LOAD ADDR. Press the Examine key (EXAM). Is MD
now 6032? Repeatedly press the EXAM and check if the MD display shows
the next opcode of the RIM loader. Note that the Memory Address display
shows the next address and not the address of the value shown in the MD
display. When you find a wrong value, set SR to the address of the wrong
value, press LOAD ADDR, set SR to the correct opcode and press DEP. Then
repeat the RIM loader check.
Load the BIN loader from paper tape:
Go to the ASR 33 Console Teletype and load the file
“BIN Loader (RIM Format)&rdquo (included in the simulator distribution)
into the reader of the teletype and turn the reader on. Go to the
KC8-EA Console, set SR to 7756 and press LOAD ADDR. Press the Clear
key (CLEAR) and then the Continue key (CONT) to start the PDP-8. The BIN
loader tape is read in. When the progress bar in the teletype window
disappears, press the Halt switch (HALT). Operate HALT again to return
it to its upper position.
Load the demo program “rotate.bin” using the BIN loader:
Go to the ASR 33 Console Teletype and load the file “rotate.bin”
into the reader of the teletype and turn the reader on. Go to the KC8-EA
Console, set SR to 7777 (start address of the BIN loader) and press LOAD
ADDR. Press CLEAR, then CONT. The paper tape is read in until the PDP-8
halts. Now turn off the reader and unload the paper tape.
Run the rotate demo program:
Set SR to 0200, press LOAD ADDR, then CLEAR and CONT. The program runs.
Set the Indicator Selector switch to AC, then watch AC and modify the
Switch Register. For the sort feature of the program, go to the ASR 33
Console and type some 4-digit positiv octal numbers, then the $ key.
Your numbers become printed in sorted order. For further information
about the rotate demo program, read the comment and source code of the