SBC PCD2.M5 Series - Memory Space on the PCD; General

Hardware Manual for the PCD2.M5 Series│Document 26/856; Version EN 12│2014-07-24
Saia-Burgess Controls AG
Memory space on the PCD
PCD2.M5_ Classic CPUs and expansion housings
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3.12 Memory space on the PCD
3.12.1 General
ThePCDcontrollersarettedwithauserprogrammemoryandamatchinguser
backup memory as standard. On the PCD, both types are referred to as user
memory.
User Program Memory (RAM)
TheuserprogrammemoryconsistsofaRAM(RandomAccessMemory)and
contains the program code and a text and DB memory area. It also contains the
extensionmemory,whichalsoholdsDBsandtexts(addresses≥4000).OnaPCD2.
M5_, all DBs and texts are always in RAM. The main difference between the texts
and DBs in the text/DB memory segment and those in extension memory is the
greater maximum size of DBs and texts.
TorunanapplicationonthePCD,itissufcienttoloadonlytheuserprogram
memory.AsthisisaRAM,theprogramandthecontentsofthetextsandDBs(and
theothermedia,registers,agsetc.)maybelostifthereisnopowerandthebattery
isatornotconnected.
Backup memory (Flash)
Inordertopreventthelossoftheprogram,everyPCDCPUhasonboardash
memoryttedasstandardtobackuptheuserprogrammemory.
ItisalsopossibletosaveDBsonthisashduringruntime.Thisallowskeyvaluesof
registersandagstobesavedtotheashatruntimeandreloadedlater.
Evenwithbackuptotheashcard,thesourcelesfortheprojectmustberetained,
as the application is only stored in the PCD as machine code.
IfittranspireswhenthePCDisstartedupthattheRAMmemoryhasbeencorrupted(e.g.
afterapowerfailurewithaatormissingbattery),theapplicationisautomaticallyreloaded
fromtheashbackupmemory.TheLISTcommand"Test"andoperand"400"canbeusedto
test this.
Allhardwaresettingsarealsosavedtotheashbackupmemory(onboardoronan
equivalentashcard).
Partition of user backup memory
Theuserbackupmemoryissplitintotwoparts.Therstisavailablefortheuser
programbackupandisalwayspresent.InthePG5hardwarecongurator,this
memory is referred to accordingly as "user program backup".