User guide

eWON 500-2001-4001-4002 User Guide - IO Servers Configuration
eWON 500®2001®4001®4002® Version 4_3_0 - User Guide - 10/5/05 - ©ACT'L sa - Page 113
6.11 MEM IO Server
6.11.1 Introduction
The MEMORY IO Server is not a real IO server because values do not come from a peripheral. Memory Tags (Tags defined with the MEM IO
server) are rather sorts of variables that can be modified by user input or by a BASIC application.
These Tags are very useful for combining different Tags and consider the result as an actual Tag, thus having data logging capabilities and alarm
management capabilities like for all other Tags.
6.11.2 Setup
There is no setup for the MEM eWON IO server.
6.11.3 Tag name convention
If no topic is specified, the Tag is a standard memory Tag. Its value is set to 0 when the eWON boots and the Tag is read/write,
it can be updated through user actions with script or web pages.
Important: RET values are saved to FLASH memory, this is not an immediate operation and the FLASH memory can only be written
and erased a limited (even if huge 1.000.000) number of times. This means that you should not use a BASIC script for changing
retentive values at very high rate. 1 Tag/Sec. is a maximum AVERAGE rate (occasional higher rates are no prohibited at all).
IO Server configuration
IO Server Name MEM
Topic Name
If no topic is specified, the Tag is a standard memory Tag.
Its value is set to 0 when the eWON boots and the Tag is read/write, it can be
updated through user actions with script or web pages
RET
If topic is set to RET, the Tag is retentive, each change is saved to flash and
when the eWON boots, the last value of the Tag is restored.
This feature can be used to use Tags as parameters.
Item Name DON’T CARE
The MEM "Item Name" is "don't care", the Tag name is automatically copied
in the MEM address by the eWON, user can change it but value will
immediately be overwritten again by the Tag name.
Table 81: MEM IO server Tag name convention