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Baud Rate - The transmission speed of data through an asynchronous channel. Often confused with BPS (bits per second), baud rate actually refers to the number of signals per second. Because each signal can represent more than one bit of data, the number of bits per second is usually higher than the baud rate. For example, 2400 bps is typically sent at a rate of 600 baud.


Binary File - A file that contains data or program instructions written in ASCII and extended ASCII characters.


ASCII - An acronym for American Standard Code for Information Interchange. ASCII files are plain, unformatted text files that are understood by virtually any computer. Windows Notepad and virtually any word processor can read and create ASCII files. ASCII files usually have the extension .TXT (e.g., README.TXT).


Bytes - A collection of eight bits that represent a character, letter or punctuation mark.


COM port - Short for a serial communication port. Most DNC software communicate with a computer through a communication port, and most IBM and IBM-compatible computers support up to four serial ports COM1, COM2, COM3 and COM4. Additional ports can be added by adding additional hardware.


CNC - Computerized Numerical Control Refers to machine tools that have a computer and memory to control their operation. Most all non manual machine tools sold today will be CNC. see also NC.


Data bits - A group of bits (1's and 0's) that represent a single character or byte. Typically, there are seven or eight data bits. During an asynchronous communication (e.g., BitCom connecting to CompuServe), each side must agree on the number of data bits. Data bits are preceded by a start bit and followed by an optional parity bit and one or more stop bits.


DNC – Acronym that can mean Distributed Numerical Control or Direct Numerical Control depending upon the application. In the beginning DNC stood for Direct Numerical Control. A computer provided machine instructions for a NC milling machine that were transmitted over telephone lines. Later the term DNC evolved to mean a system where a group of CNC machines are linked to a central computer. Or conversely a combination of computers are each linked to one or more CNC machines and the computers are linked together by way of a local area network. Distributed Numerical Control where by NC programs are sent (distributed) to the memory of a CNC machine. The program is then run from the CNC memory.


Flow control - A method of controlling the amount of data that two devices exchange. In data communications, flow control prevents one modem from "flooding" the other with data. If data comes in faster than it can be processed, the receiving side stores the data in a buffer. When the buffer is nearly full, the receiving side signals the sending side to stop until the buffer has space again. Between hardware (such as your modem and your computer), hardware flow control is used; between modems, software flow control is used.


Handshaking - Is the way in which the data flow between computers/hardware is regulated and controlled. Two distinct kinds of handshaking are described: Software Handshaking and Hardware Handshaking. An important distinction between the kinds of signals of the interface is between data signals and control signals. Data signals are simply the pins which actually transmit and receive the characters, while control signals are everything else.


NC - Numerical Control The operation of a machine by a series of coded instruction's that consist of numbers and letters of the alphabet and other symbols. These are translated into pulses of electrical current or other output signals that active motors and other device to run the machine. On early NC machines these signals was often delivered to the machines by using punched tape. Also, the term NC machine refers to machine tools that do not have a computer and memory installed. see also CNC.


NC File – a file containing one or more programs in the special language for Numeric Control machines.


NC Program – a set of instructions written in the machine language and saved to an NC file.


Parity - In data communications, parity is a simple procedure of checking the integrity of transmitted data. The most common type of parity is Even, in which the number of 1's in a byte of data add up to an even number, and None, in which a parity bit is not added.


PC        - abbreviation for a Personal Computer.


Punch - CNC output device - used in CNC machines to output programs to perforated tape. Units can be parallel to tape punch or serial output.


RS232, RS423, RS422 AND RS485 - The Electronics Industry Association (EIA) has produced standards for RS232, RS423, RS422, and RS485 that deal with data communications. EIA standards where previously marked with the prefix "RS" to indicate the recommended standard. Presently, the standards are now generally indicated as "EIA" standards to identify the standards organization.


Electronic data communications will generally fall into two broad categories: single-ended and differential. RS232 (single-ended) was introduced in 1962. RS232 has remained widely used, especially with CNC control builders. The specification allows for data transmission from one transmitter to one receiver at relatively slow data rates (up to 20K bits/second) and short distances (up to 50' @ the maximum data rate). This 50' limitation can usually be exceeded to distances of 200' or more by using low capacitance cable and keeping the data rates down to 9600 baud and lower.


RTS/CTS Hardware handshaking - uses additional wires to tell a sending device when to stop or start sending data. DTR and RTS refer to these Hardware handshaking lines. you can select whether you need to use DTR or RTS individually, or use both lines for hardware handshaking. See also Xon/Xoff.


Stop bits - In data communication, one or two bits used to mark the end of a byte (or character). At least one stop bit is always sent.


Upload - To send one or more files from your computer's disk storage to a remote computer. In DNC this usually means from the CNC machine's control back to the DNC computer. This can also mean from your computer's disk to a remote computer, such as another PC or an online service or the internet.