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The BlunkBox™

LAPB Protocol Tester

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

Four applications are:

  • Interpreter - Forth-like interpreter accepts user commands to make or break LAPB connections, send buffers as LAPB I-frame data, print statistics, etc. Macro capability allows definition of new commands. Contents of I-frame data buffers are edited using built-in hexadecimal/ASCII line editor or downloaded serially over the RS-232 terminal connection. Buffer contents can be saved to non-volatile memory.

  • Source - makes a connection and endlessly transmits I-frame packets of varying size.

  • Bounce - makes a connection and endlessly re-transmits all received I-frames.

  • BERR Test - makes two connections, comparing I-frames sent on one interface with those received on the other.

Following parameters can be configured with a built-in menu (All settings are saved in non-volatile memory):

  • LAPB T1, T2, and T4 timers, N2 retry counter, window size, and addressing (DTE or DCE)

  • TCLK source (TCLK pin, RCLK pin, or internal baud rate generator driving ECLK output), RCLK source (RCLK pin, TCLK pin, or internal baud rate generator), data encoding method (NRZ or NRZI), and baud rate.

BlunkBox comes with built-in LAPB protocol decoder, a valuable debugging aid. When enabled, a short summary of every frame transmitted or received is displayed on the terminal interface on an ongoing basis.

BlunkBox maintains statistics on the number of connections and reconnections, the number of frames sent and received, the number of CRC errors, etc. Statistics values may be displayed using the interpreter's 'stat' command.

LAPB events can be reported on the user interface terminal. Reporting of the following events is controlled using the interpreter's 'terse' and 'verbose' commands: N2 unacknowledged SABM/SABME commands, N2 unacknowledged DISC commands, N2 RNR responses, frame reject, physical layer disconnect, and LAPB disconnect and reconnect.

BlunkBox is implemented using TargetLAPBTM and TargetOSTM, Blunk Microsystems' LAPB protocol stack and real-time operating system. Both TargetLAPB and TargetOS are available as source code products. TargetLAPB is compliant with International Standard ISO/IEC 7776:1995(E) and has been extensively tested and demonstrated interoperable with other LAPB protocol stacks.

BlunkBox is shipped with User's manual and one year of technical support.