Johnson Controls XP-910x - Manual (Page 25)

Configuration Guides—XT-9100 Configuration Guide 25
A DX-9100 floating point number consists of two bytes with following
format:
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
E3 E2 E1 E0 S M10 M9 M8 M7 M6 M5 M4 M3 M2 M1 M0
where: EEEE = 4 bits exponent
S = sign (1=negative)
MMMMMMMMMMM = 11 bits mantissa
Note: 216 = 32,768; subtracting 4 bits for the exponent, 1 bit for the sign,
and 11 bits for the mantissa leaves a maximum value of 2047 for
most numeric entries with single digit resolution.
•
A number is normalized when the most significant bit is true
(M10 = 1).
•
The value of the n.th mantissa bit (n from 0-10) is:
2 exp -(-n)
•
A number is zero when all bits of the mantissa are 0.
•
The value of a number is:
= * . * 2 exp
Examples:
1 = 1400H or B001H
-1 = 1C00H or B801H
100 = 7640H or B064H
Symbols used in the Item List:
DI. Decimal Item Address
HI. Hexadecimal Item Address
Type Item Type
R/W Read Write conditions:
R Read only Item
R/W Read/Write Item
R/W (E) Read/Write Item (EEPROM)
CNF Configuration Item (EEPROM)
Tag Label for Item or bit written within an Item
Floating Point
Numbers
Item List