ACC HDLC/LAP-B (ABM) User's Guide

Chapter 1 15
Overview
Modes of Operation
Modes of Operation
As recommended by ITU-T, the BAC class of procedure involves two
combined stations operating in the Asynchronous Balanced Mode in
either two-way alternate or two-way simultaneous (half-duplex or
duplex) point-to-point configuration. Combined stations are
characterized by the ability to send both commands and responses,
receive both commands and responses, and provide for dat a link error
recovery.
The protocol optionally provides the ability to use extended s equence
numbering (modulus 128). Extended sequence numbering is selected by
configuration options. Normal operation uses modulus 8 sequence
numbering.
Data Rates
This protocol can be used at data rates up to 76.8k baud for 8-channel
ACC multiplexer cards using the HP-PB standard backplane or128k
baud for 8-channel cards installed in the EISA standard backplane. The
HDLC LAP-B (ABM) Protocol product can also be used at higher rates
for high-speed ACC multiplexer cards, such as the 2-Channel HP-PB,
8-Channel PCI, and the 4-channel T1/E1 products with 2.048M baud
capability.
Unformatted Frame or “Pass-through” Mode
This mode is no longer available with the HDLC/LAP-B product.
The “Level 1 " protocol can be used to provide this functionality. Refer to
the Level 1- HDLC Framing P rotocol User’s Guide for details.