SBC PCD2.M5 Series - Partitioning Options for User Memory

Hardware Manual for the PCD2.M5 Series│Document 26/856; Version EN 12│2014-07-24
Saia-Burgess Controls AG
Partitioning options for user memory
PCD2.M5_ Classic CPUs and expansion housings
3-30
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3.10 Partitioningoptionsforusermemory
InthePG5hardwareconguration,theusermemoryispartitionedbydefaultinto
lines of code and texts/DBs, in a way that suits most applications.
In the case of a large program with few texts/DBs or a very small program with many
texts/DBs, the user can partition the memory manually. In order to choose an appro-
priate breakdown, the following should be noted:
 The partitioning is into "kBytes lines of code" and "kBytes text/DBs", where the
"kBytes lines of code" can only be changed in 4 kByte steps, as every line of code
occupies 4 bytes
 Theresultoftheformula(4x"kBytesprogramcells")+"kBytestexts/DBs"must
equal the effectively available user memory,
e.g. 4 x 24 kBytes + 32 Kbytes = 128 Kbytes
 Each character of a text occupies 1 byte
 Each 32-bit element of a DB occupies eight bytes in the address range 0..3999,
and the header of the DB takes up a further three bytes
 WerecommendalwaysusingDBswithaddresses≥4000.Thesecanholdmore
elements(16384insteadof384),takeuplessspace(only4bytesinsteadof8
bytesperelement,butNB,8bytesinsteadof3fortheheader)andtheaccess
time is substantially shorter.
Example of manual partitioning: