SNAX/APN Application Programming Manual

The SNALU Interface

SNAX/APN Application Programming Manual—420111-001

4-3

SNAX Header

The application is responsible for setting the various SNAX header bits in outgoing

BIUs and for interpreting them in incoming BIUs. The first nine bytes of the application

I/O buffer must always contain the SNAX header. Table 4-1 describes the format of this

header.

Figure 4-2. Exchange of Control and Data Information With the SNALU Interface

Table 4-1. SNAX Header

Field Name Bytes Description

TC Indicators 0-1 Transmission control indicators specifying normal

or expedited flow, two-step reads, and network

services RUs

Status Codes 2-3 SNAX/APN status and return codes

Sequence Number 4-5 Sequence number of incoming or outgoing BIU

Request/Response Header (RH) 6-8 SNA request/response unit header

402CDT .CDD

Application

SNAX Header

SNALU

SNAX/APN Line Handler

SNA Basic Link Unit (BLU)

Controller

Link