ST10R272L - MEMORY ORGANIZATION
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Any word- and byte-data in the internal RAM can be accessed by 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
internal RAM is 00’FDFEh. For PEC data transfers, the internal RAM can be accessed,
independent of the contents of the DPP registers, via the PEC source and destination
pointers.
The upper 256 bytes of the internal RAM (00’FD00h through 00’FDFFh) and the GPRs of
the current bank, are provided for single bit storage and are bit addressable.
3.1.1
System stack
The system stack can be defined in the internal RAM. The system stack size is controlled by
the bit-field STKSZ in the SYSCON register (see table below).
For all system stack operations the on-chip RAM is accessed via the Stack Pointer (SP)
register. The stack grows downward, from higher towards lower RAM address locations.
Only word-accesses are supported by the system stack. A stack overflow (STKOV) and a
stack underflow (STKUN) register control the lower and upper limits of the selected stack
area. These two stack boundary registers can be used, not only for protection against data
destruction, but also to implement a circular stack, with hardware-supported system-stack
flushing and filling (except for the 2KByte stack option).
The technique of implementing this circular stack is described in “Circular (virtual) Stack” on
page 305.
<STKSZ>
Stack Size (Words)
Internal RAM Addresses (Words)
0 0 0 b
256
00’FBFEh...00’FA00h (Default after Reset)
0 0 1 b
128
00’FBFEh...00’FB00h
0 1 0 b
64
00’FBFEh...00’FB80h
0 1 1 b
32
00’FBFEh...00’FBC0h
1 0 0 b
512
00’FBFEh...00’F800h
1 0 1 b
---
Reserved. Do not use this combination.
1 1 0 b
---
Reserved. Do not use this combination.
1 1 1 b
1024
00’FDFEh...00’F600h (Note: No circular stack)
Table 3 STKSZ bitfield in the SYSCON register