by AltairClone » October 13th, 2014, 5:33 pm
Interesting problem...
In your configuration, MBLe looks for the top of RAM and finds it FCFF (you have the Turnkey ROM at FD00), and therefore copies itself into RAM between FC00 and FCFF. However, the Turnkey module actually overlays a full 1K of RAM (FC00-FFFF), so when the sense switch is read, the full 1K of Turnkey address space is swapped out wiping out the re-located MBLe at FC00-FCFF.
To make it work, force a PROM at FC00:
1) Upload a PROM .hex file (e.g., DBL.HEX) to an empty PROM "slot" in the clone (label it "End of RAM")
2) Use the "Change Load Address" menu option to set the PROM address to FC00
This will make MBLe find the end of RAM at FC00 instead of in the middle of the Turnkey board.
The Clone allows PROMs to overlay RAM on 256 byte boundaries, but if the Turnkey module is enabled, I need to force FC00-FFFF to be PROM no matter what is loaded in the PROM table.
Mike