ISDN Datasheet, PDF (3/14 Pages) Texas Instruments – ISDN Basic Rate Interface Software for the HPC16400E High Performance Data Communications Microcontroller

1 0 Architectural Description
1 1 INTRODUCTION
and I O drivers is by means of mail messages and sema-
This description defines the software required to implement
the ISDN Basic Rate Interface on the HPC family of micro-
phores which are managed by the multi-tasking HPC Exec-
utive
controllers including the HPC16400 which has onboard
This modular design and well defined intertask interface
hardware specifically designed for Data Communication and
make it easy for users to interface application-dependent
ISDN applications
software to the modules provided The services of the HPC
The software consists of the following main parts shown in
overview in Figure 1 1
 HPC Executive providing an operating environment and
services for the ISDN software and for additional applica-
Executive (mail semaphores timers memory management)
facilitate the writing of software tasks and I O drivers
These services are available to all tasks and to interrupt-lev-
el drivers
tion software written by OEM users of the HPC
1 2 2 Event-Driven State-Machine Architecture
 I O Drivers interfacing to the DMA HDLC controllers on
Telecommunication software typically involves many invo-
the HPC16400 and to the TP3420 ‘‘S’’ Interface Device
cations of the same code (one per call one per logical con-
 Data Link Layer Software implementing the CCITT
nection etc ) and requires a particular software architecture
Q 921 and X 25 link access procedures (LAPD and
LAPB)
 Network Layer Software implementing the Protocol Con-
trol Procedures defined in the CCITT Q 931 standard
 Demonstration Call Control Module allowing a develop-
ment engineer at a terminal to make and receive ISDN
phone calls which exercise the above software
 Tracer Module allowing a development engineer at a ter-
te ^{minal to monitor the operation of the above software}
 Management Entity Module
1 2 SOFTWARE ARCHITECTURAL PRINCIPLES
1 2 1 Modular Multitasking Environment
Eack layer or function is written as a separate software task
Obsole ^{Intertask communications and the interface between tasks}
tasks must be structured as event-driven state machines
Each task has one or more mailboxes and operates by pick-
ing up mail one message at a time from the mail queue
and processing the message to completion before returning
for the next mail message
Each ‘‘entity’’ within a task (each call each logical connec-
tion etc ) has a state block indicating its current state After
picking up a mail message the task identifies the entity in-
volved in the message accesses the state block for that
entity processes the message based on the state of the
entity and finally sets the state block to the new state of the
entity
FIGURE 1 1 HPC16400 Software for ISDN
2
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