B
base tag
A tag that actually defines the memory where a data element is stored.
base update period
See
Coarse Ratebaud
A unit of signaling speed equal to the number of discrete conditions or signal events per second. Where one bit is encoded on each signaling event, the number of baud is the same as the number of bits per second.
baud rate
The speed of communication between devices on a network. All devices must communicate at the same baud rate.
BCC
Block Check Character (BCC) is an error-checking method developed to improve error detection in data communications. The BCC is added to the end of each block of data before the block is transmitted.
BCD
Binary Coded Decimal. A numbering system used to express individual decimal digits (0 through 9) in a 4-bit binary notation.
best master clock algorithm
The best master clock algorithm is designed to automatically choose the clock which is technically the best. If there is a clock that is clearly a better source of time (such as a GPS-based clock), and all devices are left with default settings, the system is very likely to choose this clock as grandmaster.
bias
The offset that is usually added to an output to compensate for the fact that the engineering desired zero is not at the actual value zero.
binary
An integer value displayed and entered in base 2 (each digit represents a single bit). The value is prefixed with 2#, and is padded out to the length of the bool or integer (1, 8, 16, or 32 bits). Every group of 4 digits is separated by an underscore for legibility when displayed.
bit
The smallest storage location in memory that contains either a 1 (ON) or a 0 (OFF).
block-transfer
To move a block (64 words maximum) of data to or from an I/O module in one scan.
blue arrow
The blue arrow to the right of the operand value signifies that changing the value in this location will immediately change the value of the tag. (Controller Tag Value if online.)
Boolean operators (BOOL)
The logical operators such as AND, OR, NAND, NOR, NOT and Exclusive OR that can be used singularly or in combination to form logic statements or circuits. These operators can have an output response that is TRUE or FALSE.
The BOOL data type is an atomic data type consisting of a single bit.
Bootstrap Protocol (BOOTP)
BOOTP (Bootstrap Protocol) is a low-level protocol that provides configurations to other nodes on a TCP/IP network with DOS, Microsoft Windows, Windows NT, Windows 95, VMS, and HP UNIX platforms. BOOTP configuration files let you automatically assign IP addresses to a module. You can also obtain subnet masks and gateway addresses from BOOTP.
boundary clock
A clock that has multiple CIP Sync ports which maintains the timescale used in the CIP Sync domain. It serves as a source of time:
- It may be the grandmaster (in which case none of the ports will be in the slave state)
- It may recognize a better clock as a master and set the port on which it sees that better clock to the slave state.
Boundary clocks are not allowed to be slave-only. At most, one port is allowed to be in the slave state. All other ports will be in the master (or passive) state.
Boundary clocks do not pass along PTP sync packets. Sync packets received on the single slave port are used to set the device's internal clock. The internal clock is used as the time source for the generation of new sync packets on the remaining ports that are in the master state. This behavior may slightly degrade the accuracy of time, but has beneficial effect on reducing the communication load on the system grandmaster. It also allows PTP sync packets to be distributed to multiple network subnets.
Boundary clocks may be required when bridging between different physical networks. For example, the 1756-EN2T EtherNet/IP bridge module functions as a 2-port boundary clock between the EtherNet/IP network and the ControlBus backplane of the ControlLogix chassis.
branch
A parallel logic path within a rung of a ladder program.
bridge
An interface between links in a communication network that routes messages from one link to another when a station on one link addresses a message to a station on another link.
buffer
In software terms, a register or group of registers used for temporary storage of data, to compensate for transmission rate differences between the transmitter and receiving device. 2.) In hardware terms, an isolating circuit used to avoid the reaction of one circuit with another.
buffered data
In the context of the SynchLink protocol, buffered data is data that is fragmented and transmitted over multiple 50 ms SynchLink datagrams. Since buffered data is multiplexed over available SynchLink words, buffered data allows more data to be passed than is possible with direct data, but at a slower speed. In this way, the various SynchLink communication formats allow you to balance speed versus the quality of data transferred.
byte
A storage location in memory consisting of a group of 8 bits.
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