To Map Memory Ranges That Use Function Codes - HP 64751 User Manual

Chapter 5: Configuring the Emulator
Mapping Memory

To map memory ranges that use function codes

• Specify function codes with address ranges when mapping memory.
Memory mapper softkeys that represent the different function codes are:
supervisor
user
program
data
supervisor program
supervisor data
user program
user data
When you specify function codes with mapper ranges, the 68340 function code
outputs (FC0, FC1, FC2) are decoded to select particular blocks of memory.
Function codes let you overlay address ranges. When you specify function codes
as part of the address, the emulator memory mapper knows that overlaid blocks are
different memory regions and will define them separately.
If you specify a function code when mapping a range of memory, you must include
the function code when referring to locations in that range. If you don't include the
function code, an "ambiguous address" error message is displayed.
If you use different function codes, it's possible to map address ranges that overlap.
When address ranges with different function codes overlap, you must load a
separately linked module for the space associated with each function code. The
modules are linked separately because linker errors occur when address ranges
overlap.
When address ranges are mapped with different function codes, and there are no
overlapping ranges, your program modules may exist in one absolute file.
However, you have to use multiple load commands—one for each function code
specifier. This is necessary to load the various sections of the absolute file into the
appropriate function code qualified memory ranges. When you do this, be sure that
all address ranges not mapped (that is, the "other" memory mapper term) are
mapped as target RAM. When "other" is mapped as guarded, guarded memory
access errors (from the attempt to load the absolute file sections that are outside the
specified function code range) can prevent the absolute file sections that are inside
the specified function range from being loaded.
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