retrocmp

PDP11GUI Memory Loader window

The Memory Loader window can load data from disk files into memory addresses. It is a special Memory window. It’s intended use is to load DEC ROM images. Several file formats are recognized.

To load data, use the controls in an up-to-down sequence:

1. Choose a file format.
   (If a format is missing, feel free to contact me)
2. Depending on the file format, select one ore more disk files.
3. If the file format does not define a position for the data, choose a start address. Plain binary files require this.
4. Press “Load”, the data appears in the grid.
5. Press “Deposit all”. Data are transfered to PDP-11 memory ... this may take VERY long!
6. You can verify the correctness of loaded program code with the Disassembly window.

You can edit the loaded data in the grid. Since all memory addresses are regarded to be “new”, they are highlighted until deposited. All addresses are physical 18 bit or 22 bit addresses.

In the example above, data is loaded from a binary ROM image. Since PDP-11 is a 16 bit machine, often two 8 bit ROMs are used in parallel. So all data bits 7:0 are saved in a “low-byte” file, and bits 15:8 are saved in a “high-byte” file.

If you are connected to SimH, there’s an option to speed up the download: Right click into the grid and execute “Export as SimH script”. Save the memory content as “ \.sim”. Then goto the Terminal window and let SimH load the file by typing the command
“do \.sim”.
This is most easy if SimH is running on “localhost”.