Johnson Controls XP-910x - Manual (Page 23)

Configuration Guides—XT-9100 Configuration Guide 23
Appendix 1: SX Tool Item
Description and Tables
The following information is important when commissioning with the
SX Service Module.
Each constant, variable, or value in an XT-9100 Extension Module can be
addressed via an Item code. All Items are contained in the Item List.
Note: It is important to note that EEPROM Items can only be written
approximately 10,000 times, so that write commands from cyclical
processes in Supervisory Systems must be avoided.
A configuration comprises a set of parameters which are stored in a series
of memory locations in the XT-9100. These parameters are called Items.
Each Item is assigned an Item Address.
Active parameters such as analog values are stored in RAM.
Configuration parameters are stored in EEPROM. Data stored in
EEPROM is retained when the power is switched off.
The Item List at the end of this manual gives a brief description of each
Item available within the module.
The format of any XT-9100 Item is described by the following types:
Number: Floating point number (2 bytes)
1 Byte: Unsigned 8-bit hexadecimal number used to transfer logic
states or integer numbers 0-255
2 Bytes: Unsigned 16-bit hexadecimal number used to transfer logic
states or unsigned integer numbers
4 Bytes: Unsigned 32-bit hexadecimal number used to transfer logic
states or unsigned integer numbers
The information stored in the Items can have one of several formats:
1. Floating Point Numerical Items are real numbers, with a +/- sign.
They refer to input or output values, limit values, etc. They are
displayed and entered as numbers, with a sign and a decimal point.
These Items are shown in the Item List with “Number” in the Type
column.
2. Integer Items are positive whole numbers used as scale factors.
These Items are shown in the Item List with “1 Byte Int” in the Type
column.
General
Item Address
Item Type