User's Manual

UtiliNet® Endpoint User Guide 11-1-2006
Page 28 of 30
© Cellnet 2005
Glossary
Accumulator An accumulator is simply a counter in an RTU that records the number of times a contact
opens and closes or in the case of a form C contact, records the number of transitions from one contact to
the other (K to Y then K to Z in the meter world). Accumulators are most often used as interfaces into
metered values. Each accumulated pulse represents some metered quantity (KWH, gallons, barrels, etc.).
Analog An analog value is typically a measurement value obtained from a transducer. The transducer
interfaces to a system point to provide an input signal to an analog to digital converter. Transducers
typically output DC current signals in the 0 to 1 mA range or 4 to 20 mA range. The DC output signal of a
transducer is directly proportional to the input measurement value to the transducer. The transducer output
is the input to an analog to digital converter that transforms the DC signal to a digital count. Most analog
values are 11 or 12 bits plus sign. As an example, a typical voltage transducer accepts 0 to 150 volts AC
and outputs 0 to 1 mA. An eleven bit A/D converter would output a value of 1706 for an input value of 125
volts (125 = (1706
/ 2047) * 150).
Bit Oriented Protocol A bit oriented protocol is one that consists of a string of bits, 32 for example,
without a start bit, stop bit or parity bit. This type protocol was popular before microprocessors existed. The
string of individual bits was shifted using shift registers until 32 bits were captured and then the 32 bits
were evaluated for proper message content. Existing asynchronous UART hardware, such as the
transparent port, cannot capture bit oriented protocols without the possibility of dropping bits that may have
meaning in the definition of the protocol.
Bose Chaudhuri Hocquenghem (BCH)
BCH is another form of cyclic redundancy check used to detect transmission errors in master to RTU and
RTU to master communications. BCH checks are most often found in bit oriented protocols. Newer
protocols typically implement some form of CRC-16 or CRC-CCITT.
Byte Oriented Protocol A byte oriented protocol is a protocol that uses one or more 8 bit bytes where each
individual byte contains a start bit, one or two stop bits, and odd, even or no parity bit. Byte oriented
protocols are becoming the de facto standard for asynchronous communications. These protocols generally
take advantage of UART hardware for communications.
Color The color field distinguishes different addresses at a particular latitude and longitude. A WAN
address is composed of a latitude, longitude, and color. Color is used to distinguish multiple radios at the
same latitude/ longitude. In a network using domain routing, only color values 0 through 7 denote multiple
radios at the same latitude/ longitude. Color values 8 through 30 distinguish different domains, each
domain using a different color. A color value of 31 is a wildcard value and an address with a color value of
31 matches any address with the same latitude/longitude regardless of color. Radios are not programmed
with color 31. Color 31 is only used in addressing packets to radios.
Connectivity The quality of a radio’s communication with another radio.
Core In a network using domain routing, the core is the highway of routing radios that are used to route
between domains. There is only one set of core radios in a network.
Core Radio In a network using domain routing, radios are divided into “core” and “domain” radios. Core
radios are routing radios that serve as a highway to route packets between domains.
Cyclic Redundance Check (CRC)
CRC calculations provide a greater degree of security over a simple LRC. CRC checks reveal a higher
proportion of errors and are typically 16 bit values computed from the bit pattern of each byte of a message.
CRC calculations are performed by dividing the entire message by a known polynomial and retaining the
remainder as the check value. The same calculation is repeated at the receiving end and compared to the
received CRC value. Cellnet uses a CRC-CCITT (X^16 + X^12 + X^5 + 1) calculation with each packet
exchange in the network.
DCW Device control word programming language. The programs execute within devices and provide the
ability to control the device.
Domain In a network using domain routing, a domain is a localized region of connectivity. The radios
within a particular domain are well connected but do not have good connectivity to other domains. The
core is used to route between domains.
Domain Qualifying Radius Qualifying radius in domain routing is used to qualify radios as being in the
correct domain as the destination of a packet if there are separate domains with the same color. A domain