Texas Instruments TMS320C80, Руководство пользователя

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Emulating the ’C82’s Parameter RAMs
3-4 TMS320C80 to TMS320C82 Software Compatibility User’s Guide
3.3 Emulating the ’C82’s Parameter RAMs
The MP and PP parameter RAMs are a little more difficult to emu-
late for two reasons. First, only the first half of the 4-KB block of
memory occupied by each of the ’C82’s parameter RAMs is pop-
ulated by parameter RAM on the ’C80. Second, there are no re-
maining contiguous 4-KB blocks in the ’C80 (assuming that they
were used in emulating the data RAM).
The technique involves the emulation of three ’C82 RAMs by us-
ing six ’C80 RAMs:
To emulate ’C82: Use the ’C80:
PP0 parameter RAM PP0 parameter RAM and PP0 data RAM 2
PP1 parameter RAM PP1 parameter RAM and PP1 data RAM 2
MP parameter RAM MP parameter RAM and PP2 parameter RAM
Take three additional actions to ensure successful emulation:
-
Reinitialize each PP stack so that it starts at the end of the
emulated parameter RAM (the end of the second block).
-
Make sure that each PP stack does not exceed the bound-
aries of its RAM.
-
Keep PP2 and PP3 halted in the ’C80.
3.3.1 Emulating the PP Parameter RAMs
The PP parameter RAMs in the ’C82 are twice the size of the PP
parameter RAMs in the ’C80. The second half of each parameter
RAM is not populated in the ’C80; however, PP0 data RAM 2 and
PP1 data RAM 2 are available for your use. In many applications,
this RAM may be used in conjunction with the ’C80’s PP0 and
PP1 parameter RAMs to emulate the ’C82’s PP parameter
RAMs.
To do this, use the ’C80’s PP0 data RAM 2 to emulate the last half
of the ’C82’s PP0 parameter RAM, and use the ’C80’s PP1 data
RAM 2 to emulate the last half of the ’C82’s PP1 parameter RAM.
Access these RAMs through pointers to mask the memory ad-
dress differences between the ’C80 and ’C82.
This approach is viable as long as your application can tolerate
the fact that the RAM modules used for the emulation are not con-
tiguous.