Boolean Method: A method used in an IF clause on a FIELD or GROUP statement, or in a REPEAT UNTIL clause on a GROUP statement. A Boolean Method returns True (in which case the statement is executed) or False (in which case the statement is skipped).
BRANCH: A DecoderScript statement that causes control to be transferred out of line to another statement.
Branch Method: A method for use in a BRANCH statement that determines the target of the branch.
Byte: In this manual the term "byte" is always used in the sense of an 8-bit value (sometimes referred to as an "octet").
Custom Method: A method written by a user to serve a protocol-specific need. (cf Standard Method.)
Data object: Short for Decoder Data Object.
Decode: A decode is the display of decoded protocol frames provided by protocol analyzer programs.
Decoder: A decoder is the program used to decode a protocol. The decoder, written in DecoderScript takes protocol layers as its input and outputs the various bits and pieces needed that make up a decode.
Decoder ID: A 32-bit number that uniquely identifies a protocol within the protocol-analysis system.
DecoderScript: The language used to write decoders.
Decoder Package: A decoder package comprises everything necessary to carry a decoder from one computer to another. The heart of the package is of course the decoder itself. It may also contain a Frame Recognizer, a Frame Transformer, and other Custom Methods, etc.
Decoder Data Object: An object used to store complex inter-frame data.
Drf: Data related flag. These are flags that convey information about a byte of data. They are usually errors, but may be other things depending on the type of driver used to capture the data. For example, with serial asynchronous products, there are three Data related flags: parity, framing and UART Overrun. For data captured with the analyzer, which uses the analyzer’s driver, there are five Data related flags: USART Overrun, parity, framing, CRC and underrun.
DWord: Short for "Double Word". Used in the PC sense of a 32-bit (4-byte) quantity.
END_MAIN_PATH : A DecoderScript statement that marks the end of the main thread of executable statements in a decoder. Every decoder must include an END_MAIN_PATH statement and control should reach it coincidentally with the pointer reaching the end of the layer.
Event: A protocol-analyzer capture consists of a sequence of events. Such events include data of course but also start-of-frame and end-of-frame markers, error indications, records of signal changes, etc.
Executable Statement: A DecoderScript statement of a type that plays an active role in decoding fields. Executable statements are BRANCH, FIELD, GROUP, GROUP FIELD, and RESERVED.
Field: A field in a protocol layer.
FIELD: A DecoderScript statement that processes (decodes) a single protocol field. (See also GROUP FIELD.)
Format Method: A method used to format data or otherwise create text for display in the decode.
Frame: The basic communication package in which data is shipped.
Frame Recognizer: A program, actually a C++ class, that scans captured data, recognizes where frames begin and end, and inserts start-of-frame and end- of-frame events.
Frame Transformer: A method that does whatever is necessary to prepare a frame for further processing. This could involve removing escape characters, decrypting or decompressing the data.
GROUP: A DecoderScript statement that brackets a group of other executable statements.
GROUP FIELD: A DecoderScript statement that both decodes a protocol field and brackets a further set of executable statements.
Host Data Order: One of two systems by which multi-byte numeric values are interpreted. The first byte in the field is treated as the byte of highest significance while the last byte is given the lowest significance. (cf Network Data Order.)
Inter-frame Data: Data that is saved while decoding one frame for use in interpreting subsequent frames. Such data is saved with the StorePersistentField or StoreIndexedPersistentField methods, or, if it is more complex, with a Decoder Data Object.
Intra-frame Data: Data that is saved while decoding one layer for use in interpreting subsequent layers within the same frame. Such data is saved with the StoreIntraframeField method.
Layer: The portion of a frame governed by one protocol.
Method: A subprogram that can be called from a Decoder to process data in some way. We distinguish two classes of method, Standard Methods and Custom Methods. We also categorize methods according to the context in which they are used. Categories are: Boolean Methods, Branch Methods, Format Methods, Frame Transformers, NextProtocol Methods, Retrieval Methods, Size Methods, StartBit Methods and Verify Methods.
Ndrf: Non-data related flag. This is a two-byte bit- encoded value containing information about the state of the circuit that may or may not be related to a data byte. A good example is control signal changes in serial circuits, which can occur independent of a data byte being received.
Network Data Order: One of two systems by which multi-byte numeric values are interpreted. The first byte in the field is treated as the byte of least significance while the last byte is given the highest significance. (cf Host Data Order.)
NextProtocol Method: A method that determines information about the protocol used at the next higher layer in a protocol stack.
Nibble: A 4-bit value.
Pointer: An internal pointer that points to the first bit of the field being processed.
Qword: Short for "Quad Word". Used in the PC sense of a 64-bit (8-byte) quantity.
RESERVED: A DecoderScript statement used to define a reserved protocol field.
Size Method: A method used to determine the size of a field.
Standard Method: A method supplied with the protocol analyzer. (cf Custom Method.)
StartBit Method: A method used to determine a position within the current layer where the decoding of a field should start.
Stream: Data arrives in streams. Ethernet has only one stream, while asynchronous serial has two streams, named DTE and DCE. Knowing the number of streams is important for frame recognizers and inter-frame data methods that need to track data on a per stream basis.
Verify Method: A method used either to verify a frame check sequence or to validate the value in a field.
Word: Used in the PC sense of a 16-bit (2-byte) value.