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boards:ecb:mini-68k:start [2016/04/30 13:08]
jcoffman [File List]
boards:ecb:mini-68k:start [2016/05/01 15:28] (current)
jcoffman
Line 30: Line 30:
       * I/O writes: 2 or 3 w.s.       * I/O writes: 2 or 3 w.s.
   * The board is designed to support DMA access to on-board memory. However, there are no ECB boards at this time which use this feature.   * The board is designed to support DMA access to on-board memory. However, there are no ECB boards at this time which use this feature.
 +
 +Memory Protection:
 +
 +  * Memory protect hardware was added to the version 2 board. ​ The protect feature, if enabled, allows only supervisor mode programs to write to memory below a set limit. ​ Tests with the BIOS ROM posted on 28-Apr-2016 (see link below) indicate that the feature works with the BIOS and with CP/M of 26-Apr-2016 (part of the ROM image).
 +      * J7, J8, J9, & J10 -- all '​on'​ protects the lower 1K of interrupt vectors, and will cause a Bus Error (exception 2) on a write.
 +      * J7 off; J8, J9, & J10 on -- protects the low 4K (0x1000) of memory, which includes all of the BIOS variables. ​ This appears to be the most protective setting that works.
 +      * J7, J8 off; J9, J10 on -- protects the low 64K or memory. ​ This is too stringent for CP/M-68 programs to work, since many load at 0x1100 and appear to have variables allocated in this region.
 +  * *** If you use this memory protect feature, please report you successes and failures on the Forum. ***   JRC 01-May-2016
  
 ===== Hardware Documentation ===== ===== Hardware Documentation =====
boards/ecb/mini-68k/start.1462036130.txt.gz · Last modified: 2016/04/30 13:08 by jcoffman
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