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

Chapter 3 33

Using HDLC/LAP-B (ABM) Protocol

Request Specific Processing

Control Requests (E1/T1 card only)

All control writes to this protocol share a common format as shown in

Figure 3-1. Control writes are issued to the card using the zcntl() API

call.

Figure 3-1 Control Request Format

The first four bytes are defined a s a header:

Control Code Defines the action to be taken by this request.

Control Length The length of the data for this control request. This

data immediately follows the header.

Packet Length Some protocols allow packet data (data to be

transmittedoverthewire)tobepassedtoacontrol

write following the control request data. For this

protocol, these two bytes must be zero because the

protocol does not allow packet data within a control

write.

15 10987654321011121314

Control Code Control Length

(0)

Packet Length