SNAX/APN Application Programming Manual

ManualsBrandsHP ManualsServerHP NonStop G-Series

The CRT Interface

SNAX/APN Application Programming Manual—420111-001

2-5

Normal CDI Mode

You can also set CDI modes when you configure the LU with SCF or SPI. See the SCF

Reference Manual for SNAX/APN or the SNAX/APN Management Programming Manual

respectively for information on these configuration methods.

Normal CDI Mode

Normal CDI mode is the default. In this mode, the protocol enables the CDI under

either of the following conditions:

•

When an application in the send state issues a READ procedure call

In this case, an outbound data stream containing a null request unit (null RU) is sent

to the device. The protocol enables the CDI in this outbound header. See

Figure 2-4

•

When an application issues a WRITE procedure call to send an outbound data

stream to the device and the 3270 commands are read commands

The command (CMD) byte of the outbound data stream can be any of the following

3270 read commands: READ BUFFER, READ MODIFIED, or

READ MODIFIED ALL. The protocol enables the CDI on the same outbound data

stream.

In normal CDI mode, the WRITEREAD procedure call is only valid when used in two-

step reads. In a two-step read, the WRITEREAD must have a read count value of two.

See Two-Step Reads

on page 2-3.

Note that in Figure 2-4

, a WRITE procedure call enables the keyboard restore bit of the

write control character (WCC) byte, and a subsequent READ procedure call sends a null

request unit to the device to enable CDI. If the terminal user enters data before the

device has received this null request unit, an error occurs and data must be reentered. To

avoid this problem, use enhanced CDI mode.

Figure 2-4. Enabling CDI by a READ Procedure Call in Normal CDI Mode

204CDT .CDD

File-System

Procedure

Call

WRITE

READ

-----

CDI

Status

OFF

Data

Stream

Outbound

Null Request Unit (Outbound)

Inbound

Keyboard

Restore

Indicator