JANUS? 2020 Hand-Held Computer (4MB) - Intermec

JANUS 2020 Hand-Held Computer User’s Manual (4MB) NF BC
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Preparing Applications to Recover From Lockups
If an application becomes locked in an infinite loop, you may not be able to
terminate the application. You could warm or cold boot the reader, as
described in Chapter 9, “Booting and Resetting the Reader,” but the contents of
both conventional memory and the RAM drive would be lost.
You can make it easier for a user to recover from a locked-up application. If
you create applications in a programming language supported by the JANUS
PSK and you follow the instructions in the JANUS PSK reference manual, those
applications can check a flag called the application break bit whenever the
program calls the appropriate function.
When an application gets into a loop or is waiting for input, the user can turn
off the reader, enable the application break bit, and turn the reader back on. As
the reader resumes, your application finds the application break bit enabled
and takes appropriate action.
For the steps the user should perform when an application locks up, see
“Breaking Out of an Application” in Chapter 9.
Note: IRL programs automatically check the application break bit.
Using Reader Services in Applications
Reader Services are programs that decode bar codes, process data input and
output (I/O), configure the reader, and handle all power management for the
reader. AUTOEXEC.BAT loads Reader Services when you boot the reader. You
do not interact directly with Reader Services because they operate as part of the
reader’s system software. You can create applications that use Reader Services.
For help, see your JANUS PSK reference manual.
Reader Services include these programs:
Communications Utilities Communications Utilities are transmit and receive
functions that you can call with PSK functions or software interrupts.
Communications Utilities let the reader transmit and receive buffers or bytes of
data regardless of the communications protocol that you use.
Configuration Manager Configuration Manager maintains the reader’s current
configuration file (such as JANUS.INI), ensures that the reader operates
according to that configuration, and lets you change the reader’s configuration
file. Configuration Manager is a terminate and stay resident program (TSR)
that loads into the reader’s memory during a warm or cold boot.