XC2200 Derivatives
System Units (Vol. 1 of 2)
Memory Organization
User’s Manual
3-13
V2.1, 2008-08
MemoryX2K, V1.3
be executed concurrently whereas if they target the same flash module they are
executed sequentially with the data access as first. In the flash emulation this type of
conflict can not occur. The data and the instruction access will both incur the defined
number of wait-cycles (as if they would target different flash modules) and if they collide
at the PSRAM interface the instruction fetch will see an additional wait-cycle.
Data Integrity
The PSRAM contains its own error control. Details are described in the SCU chapter.
Write Protection
As the PSRAM is often used to store timing critical code or constant data it is supplied
with a write protection. After storing critical data in the PSRAM the register field
.PSPROT can be used to split the PSRAM into a read-only and a
writable part. Write accesses to the read-only part are blocked and a trap can be
activated.
3.4.2
Non-Volatile Program Memory (Flash)
The XC2200 provides up to 764 Kbytes of program Flash (C0’0000
H
… CB’FFFF
H
).
Code and data fetches are always 64-bit aligned, using byte select lines for word and
byte data.
Any word or byte data in the program memory can be accessed via indirect or long 16-
bit addressing modes, if the selected DPP register points to one of the respective data
pages. Any word data access is made on an even byte address. The highest possible
word data storage location in the program memory is CB’FFFE
H
.
For PEC data transfers, the program memory can be accessed independent of the
contents of the DPP registers via the PEC source and destination pointers.
Note: The program memory is not bit-addressable.
An area of 2 Mbytes is dedicated to program memory (C0’0000
H
… DF’FFFF
H
). The
locations without implemented program memory are reserved.
A more detailed description can be found in
.