Saia-Burgess Controls AG
Hardware manual for PCD3 series │ Document 26-789 ENG19│ 2018-06-29
Storage space on the PCD3
PCD3.Mxxx0 Classic CPU and expansion enclosure
3-49
3
Element
Media
Operand
Operand
extension
memory
DATA
TEXT
DATABLOCK
X
DB
0
…
3999
4000
…
8191
per data block max. 383 register
(Each DB in the extension store can
hold 16383 registers)
To run an application on this PCD3, it is sufficient to load only the User Program
Memory. Since this is RAM, the program and the contents of the texts and DBs
(as well as the other medias, registers, flags, etc.) may be lost if there is no
voltage and the battery is empty or not inserted. If no battery module is present,
such data loss can also occur with a discharged supercap.
Splitting of the user backup memory
User backup memory is divided into two parts for these systems:
● The first part is available for the user program backup and is always present.
In the PG5 hardware configurator, this memory is accordingly called User
Program Backup.
● The second part, optionally configurable in the PG5 called extension memory
backup (data backup), can be used to back up DBs and texts to the Flash at
runtime.
If a part of the backup memory is used as an extension memory backup, the available
user program backup memory will be reduced by twice the size of the extension memory
backup used. In parallel with the reduction of the user program backup memory, the user
program memory is also adjusted, so that the entire User Program Memory can always be
copied to the Backup Flash.
Available user backup memory on the onboard memory
The different versions of the PCD3 CPU have different sized user program
memories (and accordingly also user backup memories). The actually usable
memories are inherently PCD3 type dependent. As the available memory on the
PCD3 has been increased over time, there is a dependency on hardware and
firmware version (the larger memory is configurable from version 030).