TargetLAPB™

TargetLAPB from Blunk Microsystems is a full-featured ISO/IEC 7776 compliant LAPB protocol stack for use in embedded applications. TargetLAPB supports both RTOS and polling environments.

Benefits:

• Compliant with the LAPB standards document: ISO/IEC 7776:1995(E)
• Easy to Use Application Program Interface
• Reliability and Flow Control
• Programmable Window Size
• Multiple HDLC Channels
• Optional Support for ISO/IEC 13239 Compliant SREJ
• Optional Exclusion of FRMR (frame reject) Frames
• LAPB Protocol Decoder
• Optional LAPB Test Set
• Royalty-free Product License
• Source Code

TargetLAPB 2003.1, the newly released embedded LAPB protocol stack, is suited both for applications requiring strict ISO/IEC 7776 compatibility and for applications requiring high performance flow control and reliability over point-to-point networks. A significant new feature in release 2003.1 is optional support for ISO/IEC 13239 selective reject (SREJ) frames.

SREJ frames are not compliant with ISO/IEC 7776, but provide faster recovery from lost frames, particularly when the window size or transfer time is large. It is a desirable option when strict ISO/IEC 7776 compatibility is not required. Also, set asynchronous balanced mode (SABM/SAMBE) frames can be optionally sent in place of frame reject (FRMR) frames, for faster recovery from errors that drop the link.

TargetLAPB has been extensively tested and demonstrated interoperable with other ISO 7776 LAPB protocol stacks. Its easy to use application program interface includes LapbConnect(), LapbSend(), and LapbRecv(). Reliability is provided by CRC checks, frame sequence numbering, and positive acknowledgments with resends after timeouts. Flow control is provided by LAPB's sliding window protocol and receiver-not-ready (RNR) frames.

LAPB parameters T1, T2, T4, N2, window size, sequence number modulus (standard or extended), and addressing (DTE or DCE) are independently set for each channel. The following LAPB events can be reported by an optional callback function supplied to lapbInit(): N2 unacknowledged SABM/SABME commands, N2 unacknowledged DISC commands, N2 RNR responses, frame reject, physical disconnect, link reset, link reconnect, all I-frames acknowledged, and I-frame arrival.

Other features: the HDLC driver interface supports asserting and sensing modem control lines and the concurrent use of multiple point-to-point connections. Statistics are maintained on the number of connections/reconnections, number of frames sent and received, etc. and may be read and/or printed to stdout. If enabled, a short summary of every frame transmitted or received is printed to stdout on an ongoing basis, while the protocol stack runs.

TargetLAPB is royalty-free, and includes complete ANSI C source code, a user's manual, a sample application, and one year of technical support. TargetLAPB was developed using Blunk Microsystems' TargetOS^TM, but can be easily ported to another RTOS or used without an RTOS.

Blunk Microsystems also provides a Hardware/Software LAPB test set solution, The BlunkBox^TM. BlunkBox is designed to exercise the HDLC, LAPB, and application software of products containing a LAPB connection. Based on a single board computer, BlunkBox is used for both engineering development and manufacturing test. BlunkBox uses one RS-232 connection for the terminal-based user interface and two RS-422/RS-530 synchronous connections for LAPB/HDLC testing.