Additional Guidelines for IEC Hot Standby
154 840 USE 106 00 January 2003
IEC Applications
Optimization,
Continued
1. There are 64K words of state RAM as a maximum for IEC HSBY Registers in an
IEC Hot Standby application. Using as little state RAM as possible for other
purposes besides IEC HSBY Registers, allows running medium sized IEC
applications in IEC Hot Standby mode. When using the IEC application d ata very
efficiently, the size of the application can grow from medium to large.
2. To optimize an IEC application to consume as little memory as possible takes
some effort and may reduce the maintainability of the application. Ther efore y ou
should always try to reduce data memory to what is needed. The efficient use of
the State RAM, as described in the following section, should be considered
whenever possible. It provides large data memory benefits compared to the work
needed to achieve it.