SBC PCD1 Series User Manual

Saia-Burgess Controls AG
Manual Manual PCD 1 / PCD 2 Series │ Document 26 / 737 EN22 │ 2013-11-26
CPUs and expansion housings
3-35
Expansion of user memory
3
3.14 Expansion of user memory
3.14.1 Basics
The main reasons to expand the user memory for a PCD1/PCD2 are:
● Thebasememoryistoosmalltostoretheuserprogramandthetexts
● Theuserprogramandthenon-modifiabletextsanddatablocksaretobeheldin
Flash EPROM as a failsafe measure (the base memory is always RAM)
● Thebenefitsofdatablockswithaddresses≥4000aretobeused:
- up to 16,384 elements / DBs
- much lower overhead per element: 4 bytes per 32-bit value rather than 8 bytes
- much faster access
The PCD2.M170 and PCD2.M480 are equipped with 1 Mbyte of RAM as standard;
this cannot be expanded. To minimize the risk of program loss, we recommend the
useoftheoptionalPCD7.R400ashcard,whichallowstheuserprogramtobe
backed up.
The use of EPROMs to expand the user memory is obsolete and is no longer
recommended.WorkingwithFlashEPROMsismuchmoreconvenient(noEPROM
programming device required, behaves like RAM for the programmer) and just as
secure as EPROMs.
3.14.2 Memory location of the user program, the resources, texts and DBs
Depending on whether the user memory of a PCD1/PCD2 has been expanded or
not,thememorylocationofvariouspartsoftheapplicationwillvary.Whentheuser
memory is expanded by plugging in a memory chip, the user program and the text
strings/DBs with addresses < 4000 are stored in the additional plug-in chip.
ThebasememoryprovidedontheCPUisthenfree,andcanoptionallybedenedin
thehardwarecongurationas“extensionmemory”andusedtostoretextsandDBs
withaddresses≥4000.
Memory location
Contents
No expansion of
user memory
With expansion of
user memory
Resources (registers,
ags,countersetc.)
The resources are held in a separate RAM memory on
the CPU (always in the same location, buffered by the
SuperCap or the battery)
User program in base memory in additional chip in
“USER PROG” socket
1)
Texts and DBs with
addresses < 4000
in base memory in additional chip in
“USER PROG”socket
1)
Texts and DBs with
addresses≥4000
not available in extension memory
2)
1) i.e. in RAM, EPROM or Flash EPROM depending on the chip used. The use of EPROM is no longer
recommended; use Flash EPROM instead
2)Mustbedenedinthehardwareconguration
3.14.3 Exampleofamemoryconguration
Thescreenshotsbelowshowexamplesofthehardwarecongurationandassociated
softwaresettingsinPG5foraPCD2.M120(hardwareversion>=J)witha1Mbit
Flash EPROM plug-in expansion unit (item-no. 4 502 7141 0).

SBC PCD1 Series Specifications

General

Brand	SBC
Model	PCD1 Series
Category	Controller
Language	English