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BACnet Int egration Guide – DOAS_08.000 Rev 2 Page | 3

The BM S front end may have a solution already intact to pull individual bit s from an integer. A "read bit" function looks

to return what value a certain bit is in an int eger. Bit number are 0-31 in a 32-bit integer with 0 being the low est bit and

the furt hest to the right in the binary not ation of the number. Bit 31 would be the largest bit and the furthest to the left

in binary notation.

If the front end does not have a "read bit" or "bit extract" function, the binary value of individual bit s can be determined

by continually dividing the quotient of the int eger by 2, the remainder of the division is the value of the bit (0 or 1). A

function called M odulo or "mod" is commonly used to ret urn the remainder of integer division.

Equation: x = (round down(a/ 2

) )mod 2

· x is Boolean value for bit b, where 0 is inactive and 1 is active.

· a is the integer word value

· b is the bit of the binary number used as an exponent

· The result of a/ 2

should round down to a whole number, truncating the decimal. For example, 5/ 2

is 2.5,

however, only the 2 is used.

Example:

If the Device_Offline_Word (IV-8) is a decimal value of 11, the binary value would be 1011. This binary value would

mean that Space Thermostats 1, 2, and 4 are offline. The rest of the bit s in the binary number would be a Boolean value

of 0. (Please see

Binary Tables.)

· Bit 0 = 11/ 2

mod 2… this results in a Boolean of 1 or Active for bit 0.

· Bit 1 = 11/ 2

mod 2… this results in a Boolean of 1 or Active for bit 1.

· Bit 2 = 11/ 2

mod 2… this results in a Boolean of 0 or Inactive for bit 2.

· Bit 3 = 11/ 2

mod 2… this results in a Boolean of 1 or Active for bit 3.

Bit 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

Val 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 1

M odifying Equipment Operation

In addition to commanding unit occupancy, some syst em level sequences may require feedback from the BM S.

Common BM S adjusted sequences include it ems like supply air temperature reset control, demand cont rol ventilation

for multiple zones, and duct st atic pressure reset.

HEATING AND COOLING OPERATION SETPOINTS

Object Variable Description Active Text Inactive Text

Adjusting Temperature Setpoints

Controller Pr ovided Sequences – Occupied M ode

The cont roller has several st and-alone supply air temperature cont rol modes wit h set points that can be modified by the BM S. These modes include a

stat ic supply air temperat ure setpoint (no-reset) or allow s for t he supply air temperat ure setpoint to be reset based on outside air t emperat ure, space

tem perat ure, or return air temperat ure.

IV-1 Temperature_Reset_M ode

Commands the reset mode during occupied

operat ion.

1 = No Reset, 2 = Space Reset

3 = Return Reset, 4 = Outside Reset

AV-1 Temperat ure_Setpoint

Set s the temperature setpoint based on m ode

of operat ion (space set point, ret urn setpoint or

supply setpoint ).

Not applicable for outside reset.

Real, Default = 72°F

* M in = 50°F; Max = 100°F

AV-2 Temperat ure_Heat _Cool_Deadband

Heat/ Cool Setpt Deadband w hen Space or

Ret urn reset cont rol is active.

Htg Set pt = Temp Setpt - Deadband / 2

Clg Setpt = Temp Setpt + Deadband / 2

Real, Default = 4°F

* M in = 0.5°F; M ax = 20°F

[Space/ Ret urn Heating = 70°F,

Space/ Ret urn Cooling = 74°F]

* Typical range for st andard configuration unit, please verify at point min and max propert ies.