Programming Guide

Introduction
5
What is an HDLC Protocol?
As explained in the RFID Reader Programming Overview
section, CHUMP is a High Level Data Link Control (HDLC)
protocol. HDLC is a class of general purpose protocols that fall
within the Data Link Layer (Layer 2) of the Open Systems
Interface (OSI) reference model. See Figure 2.
Figure 2 - Open Systems Interface Reference Model
Layer 2 provides a means to transfer data between network
entities and correct transmission errors. The layer provides for
activation, maintenance, and deactivation of data link
connections, grouping of bits into characters and message frames,
character and frame synchronization, error control, media access
control, and flow control. Ethernet is a well known data link
protocol.
Unlike Ethernet, which is generally used on Local Area Networks
(LANs), HDLC protocols are primarily used on slower serial
networks.