2.1.1.2
I/O Point Limitation
Total number of I/O hardware points, including those communicated over a
LAN, used by a single stand-alone digital controller, including I/O
expansion units shall not exceed 48.
2.1.1.3
Environmental Operating Limits
Provide digital controllers that operate in environmental conditions
between 32 and 120 degrees F.
2.1.1.4
Stand-Alone Control
Provide stand-alone digital controllers.
2.1.1.5
Internal Clock
Provide a clock with each stand-alone controller. Each controller shall
have its clock backed up by a battery or capacitor with sufficient capacity
to maintain clock operation for a minimum of 72 hours during power outage.
2.1.1.6
Memory
a.
Provide sufficient memory for each controller to support required
control, communication, trends, alarms, and messages
b.
Memory Protection: Programs residing in memory shall be protected
either by using EEPROM, flash memory, or by an uninterruptible
power source (battery or uninterruptible power supply (UPS)). The
backup power source shall have sufficient capacity to maintain
volatile memory during an AC power failure. Where the
uninterruptible power source is rechargeable (a rechargeable
battery), provide sufficient back-up capacity for a minimum of
seventy-two hours. The rechargeable power source shall be
constantly charged while the controller is operating under normal
line power. Where a non-rechargeable power source is used,
provide sufficient capacity for a minimum of two years accumulated
power failure. Batteries shall be replaceable without soldering.
2.1.1.7
Inputs
Provide input function integral to the direct digital controller. Provide
input type(s) as required by the DDC design. For each type of input used on
high-level controllers, provide at least one similar spare input point per
controller.
a.
Analog Inputs: Allowable input types are 100 ohm (or higher)
platinum RTDs, thermistors, 4 to 20 mA, and 0-10 VDC. Thermistor
and direct RTD inputs must have appropriate conversion curves
stored in controller software or firmware. Analog to digital
(A/D) conversion shall have 10-bit minimum resolution.
b.
Digital Inputs: Digital inputs shall sense open/close, on/off, or
other two state indications.
2.1.1.8
Outputs
Provide output function integral to the direct digital controller. Provide
output type(s) as required by the DDC design. For each type of output used
SECTION 15910N
Page 25
Previous Page
