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XC2200 Derivatives
System Units (Vol. 1 of 2)
Memory Organization
User’s Manual
3-9
V2.1, 2008-08
MemoryX2K, V1.3
3.3
Data Memory Areas
The XC2200 provides two on-chip RAM areas exclusively for data storage:
•
The
Dual Port RAM (DPRAM)
can be used for global register banks (GPRs), system
stack, storage of variables and other data, in particular for MAC operands.
•
The
Data SRAM (DSRAM)
can be used for system stack (recommended), storage
of variables and other data.
Note: Data can also be stored in the PSRAM (see
). However, both data
memory areas provide the fastest access.
Depending on the device additional on-chip memory areas may exist with the special
purpose to retain data while the system power domain is switched off. The XC2200
contains:
•
The
Stand-By RAM (SBRAM)
.
•
The
Marker Memory (MKMEM)
.
Dual-Port RAM (DPRAM)
The XC2200 provides 2 Kbytes of DPRAM (00’F600
H
… 00’FDFF
H
). Any word or byte
data in the DPRAM can be accessed via indirect or long 16-bit addressing modes, if the
selected DPP register points to data page 3. Any word data access is made on an even
byte address. The highest possible word data storage location in the DPRAM is
00’FDFE
H
.
For PEC data transfers, the DPRAM can be accessed independent of the contents of the
DPP registers via the PEC source and destination pointers.
The upper 256 bytes of the DPRAM (00’FD00
H
through 00’FDFF
H
) are provided for
single bit storage, and thus they are bit addressable.
Note: Code cannot be executed out of the DPRAM.
An area of 3 Kbytes is dedicated to DPRAM (00’F200
H
… 00’FDFF
H
). The locations
without implemented DPRAM are reserved.
Data SRAM (DSRAM)
The XC2200 provides 16 Kbytes of DSRAM (00’A000
H
… 00’DFFF
H
). Any word or byte
data in the DSRAM can be accessed via indirect or long 16-bit addressing modes, if the
selected DPP register points to data page 3 (for the range 00’C000
H
… 00’DFFF
H
) or to
data page 2 (for the range 00’A000
H
… 00’BFFF
H
). Any word data access is made on
an even byte address. The highest possible word data storage location in the DSRAM is
00’DFFE
H
.
For PEC data transfers, the DSRAM can be accessed independent of the contents of the
DPP registers via the PEC source and destination pointers.
Note: Code cannot be executed out of the DSRAM.