Hardware Manual

Hardware Manual PCD 1 / PCD 2 Series│Document 26 / 737│Edition EN 15│2008-07-22

Saia-Burgess Controls AG

Expansion of user memory

CPUs and expansion housings

3

3.12.2 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.stored in the additional plug-in chip.

The base memory provided on the CPU is then free, and can optionally be defined in

the hardware configuration 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,

flags, 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”^ socket1)

Texts and DBs with

addresses < 4000

in base memory in additional chip in

“USER PROG” socket1)

Texts and DBs with

addresses ≥ 4000

not available in extension memory2)

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 defined in the hardware configuration