Texas Instruments TMS320C80, Руководство пользователя

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Emulating the ’C82’s Data RAMs
3-3 Prototyping ’C82 Code on the ’C80
3.2 Emulating the ’C82’s Data RAMs
The PP data RAMs are relatively simple to emulate since the
’C80 has four 4-KB blocks of contiguous memory in the form of
data RAMs 0 and 1 for each of its four PPs. The level of emulation
provided by this approach should be adequate for many applica-
tions.
The technique involves the emulation of four RAMs:
To emulate ’C82: Use the ’C80:
PP0 data RAM 0 PP0 data RAMs 0 and 1
PP1 data RAM 0 PP1 data RAMs 0 and 1
PP0 data RAM 1 PP2 data RAMs 0 and 1
PP1 data RAM 1 PP3 data RAMs 0 and 1
3.2.1 Emulating the ’C82’s PP0 Data RAM 0 and PP1 Data RAM 0
In the ’C82, each PP data RAM module is 4096 bytes long. The
’C82’s PP0 data RAM 0 occupies the same 4096 bytes of contig-
uous address space as the ’C80’s PP0 data RAMs 0 and 1.
Thus, the ’C80’s PP0 data RAMs 0 and 1 can directly emulate the
’C82’s PP0 data RAM 0. This approach also works in emulating
the ’C82’s PP1 data RAM 0.
3.2.2 Emulating the ’C82’s PP0 Data RAM 1 and PP1 Data RAM 1
Emulating the ’C82’s PP0 data RAM 1 and PP1 data RAM 1 is not
quite as straightforward. Only the first half of the 4-KB block of
memory occupied by each PP’s data RAM 1 is populated on the
’C80 (by the ’C80’s data RAM 2).
The simplest strategy for emulating the ’C82’s PP0 data RAM 1
is to use the 4096 bytes of contiguous RAM from the ’C80’s PP2
data RAMs 0 and 1. Since the address of this RAM differs from
that of the ’C82’s PP0 data RAM 1, accesses to this RAM need
to be directed through the use of pointers. Only the portion of the
software that initializes the pointer needs to be aware of the dif-
ference in addresses between the ’C80 and ’C82. Similarly, the
’C82’s PP1 data RAM 1 can be emulated by the ’C80’s PP3 data
RAMs 0 and 1.
Note:
In order for this approach to work, you must keep the ’C80’s PP2
and PP3 in a halted state.