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ISDN Basic Rate Interface Software

1. plication Tasks are typically fielded by an Interrupt Service Routine ISR The ISR may SEND information to the appro priate task via the system mail facility or it may signal the appropriate semaphore to schedule an I O task Output operations data heading away from Application Tasks are typically fielded by Service Request SRQ Tasks SRQ Tasks communicate directly with the hardware control regis ters to initiate output operations These tasks often work closely with their accompanying ISR for output initiation and completion Higher layer tasks send mail messages to he SRQ Tasks using the system mail facility to queue mes sages pending output The HPC ISDN Software includes three I O Device Drivers the Layer 1 Driver the Layer 2 Driver and the Terminal Driv er The functionality of these drivers is defined below De tails of particular Device Driver ISR and SRQ Task interac tions are defined in the Software User s Manual 2 3 1 Layer 1 1 O Device Driver The Layer 1 I O Device Driver provides implementation of the ISDN PHYSICAL Layer 1 for the HPC environment This Device Driver controls the NSC MICROWIRE PLUS Inter face to the NSC TP3420 S Interface Device SID and the HPC16400 onboard Serial Decoder Control of a COMBO Codec a display and a keypad has been imple mented later by either adding to this driver or using it as a model for additional drivers The primary responsibility of this driver is
2. Layer 2 link access procedure for the B channel m Layer 3 protocol control procedure for a terminal Layer management entity support Demonstration Call Control Task Task__View task exerciser and debugger Message trace capability Split frame message formatting Source code in C language December 1991 Block Diagram HPC ISDN Software UART TRACER CALL CONTROL APPLICATION HPC LAYER 3 CPU CONTROLLER 0 931 LAYER 2 CONTROLLER Q 921 DMA CONTROLLER LAYER 2 HDLC CONTROLLER DRIVER WATCH SERIAL WIRE DECODER LAYER 1 so KS TP 3420 ISDN S BUS COMBO COMBO IIT HPCT and MICROWIRE PLUS are trademarks of National Semiconductor Corporation ao HPC EXECUTIVE ee lee HPC ISDN SOFTWARE APPLICATION LAYER lt NETWORK LAYER DATA LINK LAYER ASmMEmMmorZzapre s PHYSICAL LAYER lt Aa 342Mm TL DD 10077 1 1995 National Semiconductor Corporation TL DD10077 RRD B30M105 Printed in U S A 19 01 U0D0491 N SUOIBOIUNWIWOD ezeq sOURBWIO I8g YIH J00t9LOdH 94 10 SABMPJOS 99ePj19 U 9 ey DISeg NASI 1 0 Architectural Description 1 1 INTRODUCTION This description defines the software required to implement the ISDN Basic Rate Interface on the HPC family of micro controllers including the HPC16400 which has onboard hardware specifically designed for Data Communication and ISDN applications The software consists of the follo
3. 2 6 The HPC Executive contains software elements that are necessary for HPC ISDN Applications These elements in clude a Multi Tasking Scheduler a Memory Manager a Tim er Manager and a Mail Manager The HPC Executive soft ware elements are tightly coupled and streamlined for the National Semiconductor HPC family of controllers The I O Device Drivers interface the HPC hardware ele ments to the HPC ISDN Software The Layer 1 Driver imple ments the ISDN PHYSICAL Layer 1 requirements for the HPC ISDN system The Layer 2 Driver interfaces the HPC DMA HDLC controller channels to the Layer 2 Link Access Task Scheduler MAIL MANAGER SYSTEM UTILITIES MANAGEMENT ENTITY TIME MANAGER DEMONSTRATION CONTROLLER CONTROLLER Q 921 X 25 LAYER 1 1 0 MEMORY MANAGER TERMINAL DEVICE DRIVER AND TRACER LAYER 2 1 0 CONTROLLER Q 921 X 25 TL DD 10077 3 FIGURE 2 1 HPC ISDN Software Functional Block Diagram 2 0 Functional Description Continued Procedures The Terminal Device Driver interfaces the HPC on board UART to the ISDN Software Device initialization sequences service request tasks and accompanying inter rupt service routines are all defined in the I O Device Driver section of this document The Layer Protocol Tasks implement the ISDN DATA LINK Layer 2 and the NETWORK Layer 3 requirements for the HPC ISDN system These tasks are designed to be hard wa
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5. Layer Protocol Task then returns to its mail box to pick up any subsequent mail The interface between all of the ISDN Layer Tasks is delib erately achieved via the System Mail Utilities This ensures a distinct uniform layering mechanism in the event that ap plication programmers wish to replace layers with their own implementations 2 4 1 Layer 2 Controller Task The primary job of the ISDN Data Link Layer 2 is to deliver error free sequenced data frames to the Network Layer 3 The Layer 2 Controller Task implements the following Layer 2 Link Access Procedures LAP for the HPC ISDN Software Package e LAPB per the X 25 CCITT Specification e LAPD per the Q 921 CCITT Specification e V 120 Terminal Adaption capability Since the Q 921 LAPD requirements were derived from the X 25 LAPB requirements most of the same Layer 2 Control ler Task routines can be used to implement both LAPB and LAPD Design considerations have been made to allow fu ture implementation of V 120 The Layer 2 Controller Task communicates with the Layer 2 DMA HDLC Controller Device Driver Task and the Manage ment Entity Task via the System Mail Utilities These tasks interrogate the mail message headers to determine whether to process the frames using LAPB or LAPD procedures The 2 0 Functional Description continued LPAD frames are mailed to the Q 931 Layer 3 Controller Task while the LAPB frames are mailed to the X 25 Layer 3 Task The
6. RS 1 f E LAYER 2 HDW PORTS MICROWIRE HDLC CONTROL een A UARTs EXTERNAL 1 0 NOT ON HPC DEVICES LAYER 1 HDW KEYBOARD DISPLAY H SD COMBO etc R B2 CHANNEL D DATA N TELEPHONE USER A TERMINALS R AND USERS E TIMER MEMORY MEMORY MANAGER noL e BLocks INTERRUPT HANDLER ON HPC ages saw ON HPC SID B1 CHANNEL VOICE H DATA je VOICE and 1 0 drivers is by means of mail messages and sema phores which are managed by the multi tasking HPC Exec utive This modular design and well defined intertask interface make it easy for users to interface application dependent software to the modules provided The services of the HPC 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 1 2 2 Event Driven State Machine Architecture Telecommunication software typically involves many invo cations of the same code one per call one per logical con nection etc and requires a particular software architecture 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 curre
7. and accom panying device drivers that either replace or complement the existing onboard controllers HDLC DMA Channel 1 is attached to the ISDN signaling D channel and will be referred to as the LAPD Channel HDLC DMA Channel 2 is attached to bearer channel B2 and will be referred to as the LAPB Channel The two chan nels operate independently of each other as much as possi ble Since they share the same interrupt hardware the Lay er 2 Interrupt Service Routine must poll the Message Pend ing Register and the Error Status Register to determine the source of each interrupt Both HDLC DMA channels use the HPC field separation feature for transmission and recep tion of data This feature relieves some memory concerns since it allows small memory buffers to be used for mes 2 0 Functional Description Continued sages that only have headers In the transmit direction this feature allows large contiguous buffers to be broken up into smaller send buffers without having to copy them following a header Issues specific to the HDLC DMA Channels are defined below HDLC DMA Channel 2 the LAPB Channel requires frame sizes to be nominally 130 bytes 2 bytes of header and 128 bytes of information Provision can be made for messages with up to 1026 bytes 2 bytes header and 1024 bytes of information The presentation of data between the Layer 2 Driver and Layer 2 Controller is identical regardless of which channel the frames
8. de fined in CCITT Specification Q 931 In the HPC ISDN Appli cation the Call Control Task communicates with the Layer 3 Controller Task and the Tracer Task The availability of two circuit switched voice bearer channels is simulated in the Call Control Task The Call Control Task sends standard Terminal Equipment prompts and messages to the Tracer Task where they are displayed on a UART driven CRT The Call Control Task has the following responsibilities e B Channel Resource Management 2 0 Functional Description Continued e Connection Endpoint Suffix CES Allocation e Conversion between L3 Primitives and Terminal Action The Call Control Task and the Layer 3 Controller Task com municate via the NL_DATA_REQ and NL_DATA_IND Primitives The messages that are supported between these tasks are listed below e Commands from Call Control to Layer 3 CC_SETUP_REQ CC__SETUP__RESP CC_SETUP_REJ__REQ CC__INFO__REQ Setup Request Setup Response Setup Reject Information CC_ DISCONNECT_REQ Disconnect CC_ RELEASE__REQ CC__ALERTING__REQ Release Alerting CC__BROADCAST__RESP Broadcast Response CC_ CALLPROC__REQ CC_ PROGRESS__REQ CC_ NOTIFY_REQ CC_ RESUME__RQ CC_ RESUME__REJ CC_ SUSPEND__REQ CC__SUSPEND__REJ CC__SETUP_IND CC__SETUP_CONF Call Proceeding Progress Notify Resume Resume Reject Suspend Request Suspend Reject Command from Layer 3 to Call Control Setup Setup Confirm CC__SETUP__COMP__I
9. processed de pending on the state of the network connection This pro cessing typically includes the transmission of a Primitive to another Layer Task and the appropriate update of the net work connection state block User Information 2 4 2 2 Call Suspension And Resumption Call Suspension SUSPEND requires that the Bearer Chan nel facility and the Call Reference for a call be temporarily relinquished The network connection is left intact but in the suspend state The RESUME command reactivates the call by obtaining a Bearer Channel facility and establishing a new Call Reference The Suspend function is somewhat analogous to the call HOLD feature 2 4 2 3 Call Status And Notification The Network can request the status of a network connec tion at any time via the USER INFO NOTIFY and STATUS Commands The information includes Service Validation and Channel Configuration 2 4 2 4 Layer 3 Protocol Execption Management The Layer 3 Controller is responsible for handling excep tions to the Network Control Protocol The primary Layer 3 Controller Task protocol exception is the expiry of the Layer 3 timer Such an exception requires the retransmission of the particular command and may prompt a message to the Management Entity Task 2 4 2 5 Timer Support The Layer 3 Controller supports the following system timers per CCITT Specification Q 931 T303 SETUP ACK Timer T305 DISCONNECT ACK Timer T308 RELEASE ACK Timer T313 CONNEC
10. to initialize and control the SID The higher layer ISDN tasks mail activation and deactivation messages to the Layer 1 Service Request Task This task sends the appropriate command to the SID via the MICROWIRE PLUS Interface The SID interrupts the HPC whenever it changes state The Layer 1 Interrupt Serv ice Routine fields responses when the SID changes state and mails the information to the Layer 2 Controller Task and to the Management Entity Task The Serial Decoder is initialized to MODE 4 with the ISDN D Channel terminated by DMA HDLC Channel 1 and Bear er Channel B2 terminated by DMA HDLC Channel 2 The SID can swap B1 and B2 internally to allow voice or data on either channel The Layer 1 I O Device Driver can communicate with any other Task via the System Mail Utilities 2 3 2 Layer 2 I O Device Driver The Layer 2 I O Device Driver interfaces the two HPC16400 onboard DMA HDLC channels one to the 16 kbit per sec ond D signaling channel and one to the 64 kbit per sec ond bearer B2 channel The Layer 2 Service Request Task receives Physical Layer PH Primitives from the Layer 2 Controller Task via the system mail utility The Layer 2 Inter rupt Service Routine handles block messages received from the DMA Controller and mails them as Physical Layer PH Data Primitives to the Layer 2 Controller Task This generic mail message interface allows an Application User to easily introduce external DMA and HDLC Controllers
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13. HPC16400 HDLC hardware handles the Layer 2 HDLC Procedures which includes bit stuffing address recognition and Frame Check Sequence generation and detection The Layer 2 Controller Task is responsible for the Layer 2 Data Link Procedure which includes the following functions e Data Transmission e Protocol Exception Management e LAPD Specific Functions To accomplish these functions the Layer 2 Controller sup ports the full set of Layer 2 Peer to Peer messages defined in the CCITT Specification Q 921 These messages are list ed below and defined further in the Software User s Manual Ul Unnumbered Information Frames UA Unnumbered Acknowledge SABM E Set Asynchronous Balanced Mode Extended DISC Disconnect Command DM Disconnect Mode I Acknowledged Information Frames RR Receiver Ready RNR Receiver Not Ready REJ Request Recrimination of Frames FRMR Unrecoverable Error Frame Reject The Layer 2 Controller Task also supports the primitives required to communicate with the other ISDN tasks 2 4 1 1 Layer 2 Data Transmission Layer 2 peer to peer Data Transmission is supported with two modes Unacknowledged Data Mode and Multi Frame Acknowledged Data Mode The Unacknowledged Data Mode is used primarily for setting up logical connections and for peer to peer Management Entity communication This mode uses the Unnumbered Information Ul and the Unnumbered Acknowledge UA messages The Multi Framed Acknowledged Mode
14. ISDN ISDN Basic Rate Interface Software for the HPC16400E High Performance Data Communications Microcontroller l TEXAS INSTRUMENTS Literature Number SNOS397A vationat Semiconductor ISDN Basic Rate Interface Software for the HPC16400E High Performance Data Communications Microcontroller General Description Features The ISDN Basic Rate Interface Software Package imple mented on the National Semiconductor HPC Microcon troller Family contains the software elements that are nec approved by ANSI committees for North America Multi tasking executive Preemptive scheduling Modular software design HPC physical layer I O interface E E E essary to implement CCITT standards Q 921 and Q 931 as m Multiple timer facility E E The software package is designed to be easily unbundled and used independently by a software developer Each lay LAPD er or function is written as a separate software task This gy modular design and well defined task interface make it easy LAPB to interface application dependent software to the modules provided The coding standards for software development have been designed to ensure development of consistent structured code which can be easily used and maintained over the life of the code E E This software is supplied as a disk set and is used in con z E E E endpoint junction with HPC development tools and software Layer 2 link access procedure for the D channel
15. Interface Software Package implemented on the National Semiconductor HPC Microcontroller Family Specifically the HPC16400 Software Package implements or supports the following high level functions e Multi Tasking Executive e HPC Physical Layer O Interface e Layer 2 Link Access Procedure for the D Channel LAPD e Layer 2 Link Access Procedure for the B Channel LAPB e Layer 3 Protocol Control Procedure for a Terminal End point e Management Entity Support e Call Control Demonstration Task e Message Trace Capability The HPC ISDN Software Package has been divided into several functional software elements as illustrated in the HPC ISDN Functional Block Diagram Figure 2 1 These functional elements correspond to software modules The purpose of this section is to introduce the various software elements to define their interactions and to relate their functionality to the appropriate ISDN standards where ap plicable The HPC ISDN Software Package will require additional software drivers and application specific tasks prior to serv ing as a useful ISDN Terminal Endpoint TE entity The HPC ISDN software has been coded and documented to allow easy integration of additional application code The HPC ISDN Software elements illustrated in Figure 2 1 have been divided into the following categories e HPC Executive 2 2 e O Device Drivers 2 3 e ISDN Layer Protocol Tasks 2 4 e Application Tasks 2 5 e System Utilities
16. ND Setup Complete CCI_NFO_IND CC__ALERTING_IND CC_ PROGRESS_IND CC_DISCONNECT_IND CC_ RELEASE__IND CC_ CALLPROC__IND CC_ RELEASE__CONF CC_STATUS_IND CC_ ERORR_IND CC_ RESUME__CONF Information Indication Alerting Progress Disconnect Release Call Proceeding Release Confirm Status Indication Error Indication Resume Confirm The Call Control Task also communicates with the Tracer Task using single byte keystroke like commands These commands are packaged mail messages containing two bytes the first byte is the Sender Task s ID the second byte is the keystroke command The following messages are sent between Call Control and Tracer e Keystroke Commands from Tracer to Call Control Task TR_ON__HOOK ON Hook TR__OFF__HOOK OFF Hook TR_DIGIT_1 Digit 1 TR_DIGIT_2 Digit 2 TR_DIGIT_3 Digit 3 TR_DIGIT_4 Digit 4 TR_DIGIT_5 Digit 5 TR_DIGIT_6 Digit 6 TR_DIGIT_7 Digit 7 TR_DIGIT_8 Digit 8 TR_DIGIT_9 Digit 9 TR_DIGIT_O Digit 0 TR_DIGIT_STAR Digit TR_DIGIT_POUND Digit Commands from Call Control Task to Tracer TR_IDLE Idle ON HOOK TR__DIALTONE Dial Tone TR__DIALING Dialing TR_RINGING Ringing TR__BUSY Busy TR__CONVERSATION Conversation TR__RINGBACK Ringback TR__ERROR Error 2 5 2 Management Entity Task The Management Entity Task is closely coupled to the ac companying Network Management Entity design and to the terminal hardware configuration Implementation design de cisions have been made that make t
17. T A license agreement is required for the use and sale of the National Semiconductor ISDN Software Contact your local National Semiconductor field sales office for more informa tion or contact the factory direct at National Semiconductor ISDN Software Support M S 16 174 2900 Semiconductor Drive Santa Clara CA 95051 408 721 5719 3 2 SOFTWARE ORDER INFORMATION ISDN software is available in either Object or Source Code format A Demonstration package is also available Manuals are included with the Demonstration package and with the Executive and Basic Rate Interface Software packages Basic Rate Interface BRI software is available for several different central office switches The generic BRI includes a generalized CCITT Switch Interface Each BRI Package contains the following modules Layer 1 Driver controls S device Layer 2 Driver controls DMA HDLC Layer 2 Controller Q 921 Layer 3 Controller Q 931 Protocol Control Management Entity Q 921 and Q 931 Call Control Demonstration Application Tracer Demonstration and Development Tool The Multi Tasking Executive contains two modules Executive Core Module Executive Interface Module The Executive Interface Module is always supplied as source code to allow modification to insert application tasks A Multi Tasking Executive is required to run the Basic Rate Interface Order Part Number Description Multi Tasking Executive HPC ISDN EXEC O Multi Tasking Execut
18. T ACK Timer 2 4 2 6 SDL Updates The Layer 3 Controller Task very closely follows the SDL procedures illlustrated in CCITT Specification Q 931 with a few enhancements These enhancements are listed here and fully defined in the Software User s Manual a Three new SDL States have been added to accommo date establishing the Data Link corresponding to a partic ular CES The new states are e IDLESTATE e RELEASEWAIT e ESTABLISHWAIT b The Q 931 NULLSTATE SDL now accepts a new com mand CCBROADCASTRESP This command is sent from the Call Control Task to allow transistion from the NULLSTATE 0 to the CALLPRESENT State 6 during a Network Originated call via the Broadcast mechanism 2 5 APPLICATION TASKS The Application Tasks are very dependent on both the ter minal equipment configuration and the far end Network En tity software implementation The HPC ISDN Software Package includes two sample Application Tasks the Dem onstration Call Control Task and the Management Entity Task Both of these tasks can be replaced or updated when ported to a particular application These tasks are included in the HPC ISDN Software Package primarily to verify the operation of the OSI Layer Protocol Tasks and the HPC Device Drivers 2 5 1 Demonstration Call Control Task The Demonstration Call Control Task is closely coupled to the specific facilities of an application The interaction be tween the Layer 3 Controller Task and Call Control is
19. Timer expiry also prompts a message to the Management Entity Unrecoverable exceptions result in the Frame Reject FRMR response A message to the Man agement Entity Task is also sent in this case 2 4 1 3 Layer 2 LAPD Specific Functions The following Layer 2 Controller Task functions are LAPD specific These functions involve establishing and maintain ing multiple logical data link connections Note that a LAPB connection will be maintained as a special independent logi cal connection A two byte address is required for each logical data link This address is referred to as the Data Link Connection Identifier DLCI The DLCI consists of a Service Access Point Identifier SAPI and a Terminal Endpoint Identifier TEI The Layer 2 Controller Task is responsible for sup porting the TEI Assignment Procedure and the TEI Verifica tion Procedure These procedures are both initiated by the Management Entity The Layer 2 Controller Task supports both the Automatic and Non Automatic TE Assignment Procedures Establishment of the LAPD multi frame acknowledged data transmission mode requires an extended command SABME to prompt the peer entity that the frames are in tended for a particular logical data connection identified by the accompanying DLCI The Layer 2 Controller Task main tains each logical link s state and data frames independent ly as explained earlier in this section The Layer 3 Controller Task addresses and maintains ind
20. again choose the task at the head of prioritized Ready Queue and run that task A task may change the priority of any task including itself The priority change takes place immediately to the extent that the target task s TCB is updated with the new priority and the queue in which the target task s TCB is waiting is resorted to reflect the new priority If the target task is in the Ready Queue and its new priority is higher than the priority of the running task then the target task will run once all protected sections are exited See Section 2 2 3 below 2 2 2 Semaphores A semaphore is a global variable accessed through the Ex ecutive which can be Signaled incremented by one task and Waited on by another task A semaphore is typically used to manage the sharing between tasks of some re source e g an I O device mail messages etc At any mo ment the value of a semaphore may be positve negative or zero A positive value indicates the number of resources available a negative value indicates the number of tasks waiting for resources and a zero value indicates that there are no resources available and no tasks waiting for them When a task Waits on a semaphore if the semaphore has a nonzero positive value the task will immediately go on the Ready Queue and the semaphore value will be decrement ed by one On the other hand if the semaphore has a zero or negative value the task will be queued on the semaphore and the se
21. are associated with 2 3 3 Terminal Device Driver and Tracer The Terminal Device Driver interfaces to the HPC onboard UART The associated SRQ Driver Task referred to as Tra cer serves primarily as a high level demonstration vehicle Tracer can field mail messages from any other task in the system as well as keystroke mail messages from its accom panying ISR Tracer s responsibilities include the following functions e Management of the Telephone Simulation User Inter face e Display Management of the System Trace Mail Mes sages e Proper Display of Task Related Information The Telephone Simulation function of Tracer allows the user to enter telephony like keystroke characters that are passed to Tracer then on to the ISDN layer tasks for pro cessing Menu responses are fielded by Tracer to select various levels of the Trace function as well as to enter and exit the Telephone Simulation mode Depending on the level of trace that is selected Tracer re ceives mail messages from the system tasks and properly formats them on the CRT display Tracer offers various lev els of trace capability Trace can be turned off all together in which case only the application layer Telephone Simula tion inputs will be displayed Trace can display all messages from every layer or it can be set to zoom to display only the messages at a particular layer Messages will generally have address fields and data fields The Ter
22. e pendent logical connections via an identifier called a Con nection Endpoint Suffix CES Since the CES is different from the Layer 2 Terminal Endpoint Identifier TEI a map ping function is required The Layer 2 Controller Task main tains a CES TEI translation procedure to properly address Layer 3 logical entities 2 4 2 Layer 3 Controller Task The Layer 3 Controller Task implements the application in dependent portion of the ISDN NETWORK Layer 3 protocol per the Q 931 CCITT Specification The primary responsibili ty of the Layer 3 Controller Task is to establish a network access connection link between a terminal and its peer in the Central Office The Layer 3 Controller Task communicates with both the Layer 2 Controller Task and the Call Control Task by send ing primitives via the System Mail Utilities The Layer 3 Con troller Task also communicates with the Management Entity Task The HPC ISDN Layer 3 Controller Task is responsible for the following NETWORK functions e Call Establishment and Clearing e Call Suspension and Resumption e Call Status and Notification e Protocol Exception Management 2 0 Functional Description Continued The Layer 3 Controller Task supports all the Network Layer Peer to Peer messages defined in the CCITT Specification Q 931 i e e Call Establishment and Clearing Messages ALERT Alerting CALL PROC Call Proceeding CONN Connect CONN ACK Connect Acknowledge INFO Informati
23. ects of this are not handled in the version of Q 931 on which the Layer 3 Task is based Therefore additional Layer 3 states and SDL diagrams have been created and addition al software has been written to handle this requirement 1 5 ISDN TELECOMMUNICATIONS SOFTWARE The software packages described below are designed to be easily unbundled and used independently by a software developer 1 5 1 Layer 1 I O Driver The Layer 1 I O Driver controls the HPC MICROWIRE PLUS interface and the onboard Serial Decoder This driver is responsible for the hardware initialization the con trol of the Serial Decoder the activation and the deactiva tion of the Layer 1 I O device Use of the HPC Executive mail and semaphore services makes this driver simple to implement and easy to enhance by users that require addi tional Layer 1 hardware interfaces 1 5 2 Layer 2 I O Driver The Layer 2 I O Driver controls the HDLC DMA controllers onboard the HPC16400 and interfaces this hardware to the Layer 2 Task This driver is responsible for the hardware initialization the reception of frames toward the HPC the transmission of frames away from the HPC and appropriate error handling Use of the HPC Executive mail and sema phore services makes this driver simple to implement and easy to replace with alternative drivers that a user may wish to develop 1 5 3 Layer 2 Task The Layer 2 Task implements the full LAPD protocol de fined in Q 921 p
24. ed from the system by waiting on a semaphore which is typically never signaled 2 6 2 Nonmaskable Interrupt NMI Handler Since terminal power is generally a concern the HPC can go into an idle low power mode when the Terminal Equip ment is idle In this mode the HPC is awakened via an NMI prompted by a local off hook indication or by a far end line 10 2 0 Functional Description Continued signal detection signal from the SID Conditions for deter mining when to go in and out of idle mode are application dependent 2 6 3 Timer Interrupt Handler The Timer Interrupt Handler fields interrupts from two of the HPC onboard timers Timer TO the Watchdog Timer over flows every 65536 clock counts When this occurs the Timer Interrupt Handler mails a message to start the Watchdog Task Timer T1 the ISDN Software Timer overflows every 10 ms The ISDN Software Clock is incremented every tenth Timer T1 overflow resulting in an ISDN Clock with 100 ms resolution which is used by the Executive Timer facility 2 6 4 Watchdog Task A special task is performed by the HPC s watchdog feature to verify system sanity The Watchdog Task waits for a mail message that is sent by the Timer Interrupt Handler when Timer TO overflows This operation requires that the Watch dog Task be regularly scheduled by the HPC Executive The Watchdog Task is assigned the highest task priority 255 3 0 Ordering Information 3 1 LICENSE AGREEMEN
25. ently running task then as soon as the currently running task emerges from all critical sections and non preempt sections the currently running task will stop running The task that was moved to the Ready Queue will run The preempted task will be placed on the Ready Queue in the normal manner 2 0 Functional Description Continued Executive functions allow preemption to be selectively turned on or off by task or for an entire application 2 2 4 Time Slicing Time slicing modifies the task scheduling algorithm as fol lows at each tick of the timer clock the clock which also controls the time out timers if the currently running task has the same priority as the task at the head of the Ready Queue then if the currently running task is not in a non pre empt section it will stop running and the task at the head of the Ready Queue will run The task that stops running is placed on the Ready Queue in the normal manner i e after all tasks of equal priority Time slicing enables the Executive to share the processor equally between tasks of equal prior ity 2 2 5 Mailboxes and Mail Messages The main form of intertask communication is the sending and receiving of mail Mailboxes exist independently of tasks any task may send mail to any mailbox and any task may read mail from any mailbox However in a typical sys tem each task has one mailbox from which it reads all its mail and to which other tasks send mail de
26. f Microcontrollers Com plete information on Development Systems and Accesso ries may be found in the Microcontroller Development Sup port Datasheet 11 ISDN Basic Rate Interface Software for the HPC16400E High Performance Data Communications Microcontroller LIFE SUPPORT POLICY Lit 105300 NATIONAL S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF NATIONAL SEMICONDUCTOR CORPORATION As used herein 1 Life support devices or systems are devices or systems which a are intended for surgical implant into the body or b support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided in the labeling can be reasonably expected to result in a significant injury to the user 2 A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system or to affect its safety or effectiveness National Semiconductor Corporation 1111 West Bardin Road Arlington TX 76017 Tel 1 800 272 9959 Fax 1 800 737 7018 National Semiconductor Europe Fax Email Deutsch Tel English Tel Frangais Tel Italiano Tel 49 0 180 530 85 86 cnjwge tevm2 nsc com 49 0 180 530 85 85 49 0 180 532 78 32 49 0 180 532 93 58 4
27. he Management Entity Task unique to a particular application while still following the general requirements of the CCITT Specifications Modi fications will be required in the Management Entity Task prior to its successful operation in a particular application environment The Management Entity Task that is included in the HPC ISDN Software Package presumes a particular hardware configuration and Central Office Software imple mentation The Management Entity Task communicates with the Layer 3 Controller Task the Layer 2 Controller Task and the Lay er 1 Device Driver Task via the System Mail Utilities The Management Entity Task has the following responsibili ties e Initialization of the Terminal Equipment e Configuration of the Terminal Equipment e TEI Assignment and Verification e Multiple Error Notification e Unrecoverable Error Notification e Activation Deactivation of the Terminal Equipment 2 6 SYSTEM UTILITIES The system utilities initializes the HPC system upon power up and provide support for various machine specific fea tures of the HPC 2 6 1 Power Up Reset Main Task This task is the entry point upon system power up The Main Task is responsible for Initializing the general HPC Hardware Initializing the HPC Executive Data Structures Queuing up the Tasks on the Ready Queue The Main Task starts with the highest priority 255 After running the Main Task has served its purpose and is re mov
28. ifications The Layer 2 Controller Task satisifies the Link Access Procedures for both the D Channel and the B Channel LAPD and LAPB Design considerations have also been included for the future implementation of V 120 the new CCITT rate adaption scheme The Layer 2 Controller Task s data frame delivery service allows the Layer 3 Controller Task to confidently setup and teardown user voice and data calls on the available facili ties The Layer 3 Controller Task uses CCITT Specification Q 931 as the primary functional specification Note that the X 25 Layer 3 packet processor task is not included in the initial software package The Layer Protocol Tasks require a somewhat non conven tional task architecture in order to simultaneously manage a significant number of multiple logical connections This event driven state machine architecture requires that a state memory block be created and maintained for each logical connection When a Layer Protocol Task wakes up due to the arrival of mail the message s address is interro gated to determine which logical connection is to receive the mail The particular logical connection s state block is retrieved and the mail message is processed per the CCITT Specification requirements depending on the state of the particular logical connection Typically processing the mail message results in sending a Primitive message to another task and updating the logical connection s state block The
29. is established by the Set Asynchronous Balanced Mode SABM command This mode provides the mechanism for acknowledgement of data frame transport in each direction The Multi Frame Ac knowledged Mode is terminated with the Disconnect DISC command The response to the DISC message can be ei ther an Unnumbered Acknowledge UA message or a Dis connect Mode DM message The actual Layer 2 data frames are transmitted in the Information I messages while in the Multi Framed Acknowledged Mode The Layer 2 Controller is responsible for avoiding message congestion and buffer overflow A Layer 2 entity can issue the Receive Ready RR command to its peer to indicate that it is ready to continue data transmission Likewise the Layer 2 Controller can issue the Receiver Not Ready RNR command to its peer to indicate that it is not ready for data transmission 2 4 1 2 Layer 2 Protocol Exception Management The Layer 2 Controller Task is responsible for handling ex ceptions to the Data Link Protocol These exceptions are of two types recoverable and unrecoverable Recoverable ex ceptions in the receive direction are typically failed frames which are handled by requesting the retransmission of the failed frame with the Reject REJ command Recoverable exceptions in the transmit direction include the expiry of a Layer 2 Timer Timer expiry requires the retransmission of the frame that was not acknowledged in time and all subse quent frames
30. ive Object Code Basic Rate Interface HPC ISDN BRI S Basic Rate Interface Generic Source Code HPC ISDN BRID S_ Basic Rate Interface DMS 100 Source Code HPC ISDN BRI5 S Basic Rate Interface 5ESS Source Code Demonstration Package HPC ISDN PCDEMO ISDN Basic Rate Interface Demon stration includes Multi Tasking Exec utive and Basic Rate Interface Soft ware Manuals 4 0 Other Related Information 4 1 DEVICE INFORMATION Additional technical information on devices referenced in this datasheet is available from National HPC16400 High Performance microController HPC16083 High Performance microController TP3076 COMBO II TP3420 CCITT S T Interface 4 2 DEVELOPMENT SUPPORT INFORMATION Development tools are available for the HPC Family of Mi crocontrollers These tools support the ISDN development environment ISDN software must be ordered separately 4 2 1 ISDN Demonstration Kit A kit is available that demonstrates the software and hard ware discussed in this datasheet Included in this kit is a TP3500 development board featuring the HPC16400 TP3070 COMBO II TP3420 SID and ISDN Basic Rate Interface software in ROM A complete set of manuals are included This demonstration kit may be ordered from Na tional part number ISDN TP3500 Kit 4 2 2 Development Systems Several different Microcontroller On Line Emulator Devel opment Systems are available for hardware and software development of the HPC Family o
31. maphore value will be decremented by one When a task Signals a semaphore the semaphore s value is incremented by one and the highest priority task waiting on the semaphore is put on the Ready Queue A common use for a semaphore is the management of a non shareable resource such as an I O device When the device is available the associated semaphore has the value 1 When a task wishes to obtain exclusive use of the de vice it Waits on the semaphore which is then decremented to 0 with the task going immediately back on the Ready Queue If another task then attempts to use the device its Wait call will cause it to be placed on the Semaphore Queue and the value of the semaphore will be decremented to 1 Other tasks may also Wait on the semaphore each decre menting its value by one The negative value of the sema phore indicates the number of tasks Waiting for the device The waiting tasks are ordered in the semaphore queue ac cording to their priority When the first task is done with the device it Signals the semaphore which moves the first wait ing task to the Ready Queue and increments the sema phore or if there are no waiting tasks returns the sema phore to its original value of 1 2 2 3 Preemptive Scheduling Preemptive scheduling enables the executive to respond quickly to high priority events If a task that is waiting on a Semaphore Queue modes to the Ready Queue and if that task is of higher priority than the curr
32. minal Driver s Interrupt Service Routine ISR han dles keyboard characters from the UART and mails them to the Tracer SRQ Task for further processing The ISR also handles transmission completion of a character that has been sent to the CRT The data structures and hardware interface requirements for the Terminal Device Driver and capabilities of Tracer are defined in the Software User s Manual 2 4 ISDN LAYER PROTOCOL TASKS The ISDN Layer Protocol Tasks provide implementation of the DATA LINK Layer 2 and the NETWORK Layer 3 in ac cordance with the protocol definitions of the CCITT Specifi cations The two Layer Protocol Tasks the Layer 2 Control ler Task and the Layer 3 Controller Task are designed to satisy the ISDN Basic Rate Interface BRI Terminal Equip ment requirements They are independent of user applica tions and hardware environment The PHYSICAL Layer 1 implementation is defined in the I O Device Driver section of this document Implementation of layers above the NET WORK Layer 3 are specific to user applications Two such layer tasks are provided the Demonstration Call Control Task and the Management Entity Task These tasks are defined in the Application Task section of this document The purpose of the Layer 2 Controller Task is to provide the NETWORK Layer 3 with an error free sequenced data frame service The Layer 2 Controller Task uses CCITT Specifications Q 921 and X 25 and the primary functional spec
33. nt 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 TRACER TASK LAYER 3 TASK Q 931 PROTO CONT LAYER 2 TASK LAPD Q 921 M A N A G E M E N T SERVICE REQUEST INTERRUPT HANDLER HANDLER SERVICE REQUEST INTERRUPT HANDLER HANDLER i ry LAYER 2 HDW NOTE HDLC CONTROL TIMER UART THE SYMBOL LMB REPRESENTS AN INTERTASK MAILBOX D CHANNEL SIGNALLING TERMINAL TRACER AND DEMO j SIGNALLING mja TRACER TL DD 10077 2 FIGURE 1 1 HPC16400 Software for ISDN 1 0 Architectural Description Continued 1 2 3 Coding Standards The coding standards for software development have been designed to ensure development of consistent structured code which can be easily used and easily maintained over the life of the code 1 3 HPC EXECUTIVE The HPC Executive provides an operating environment for the Layer 2 and Layer 3 tasks the application tasks the various support tasks and the I O drivers which interface to the hardware It provides the following services to the tasks and 1 0 drivers e Scheduling of tasks that are ready to run based on task priority Preemptive scheduling and time slicing can be optionally enabled Task task and d
34. on PROG Progress SETUP Setup SETUP ACK Setup Acknowledge DISC Disconnect REL Release REL COM Release Complete e Call Suspension and Resumption Messages RESUME Resume RESUME ACK Resume Acknowledge RESUME REJ Resume Reject SUSPEND Suspend SUSPEND ACK Suspend Acknowledge SUSPEND REJ Suspend Reject e Miscellaneous Messages NOTIFY Notify STATUS Status STATUS EN Status Enquiry USER INFO 2 4 2 1 Call Establishment And Clearing The Layer 3 Controller Task s primary responsibility is to establish and clear user network connections on available bearer channel facilties The Q 931 CCITT Specifications include Call Establishment and Clearing of both circuit switched and packet switched calls Initially the HPC ISDN Software Package only supports circuit switched call proce dures on Basic Rate Interface BRI Bearer Channels The Layer 3 Controller Task is responsible for Call Reference assignment and maintenance The Layer 3 Controller Task supports Call Establishment using both the Overlap and Non Overlap enbloc addressing modes The procedure for establishing and clearing network con nections is defined in CCITT Specification Q 931 It is impor tant to note that the Layer 3 Controller Task maintains an associated state block for each network connection Primi tive mail messages arriving at the Layer 3 Controller Task will be interrogated to determine which network connection is to receive the mail The mail message is
35. oted to defining each of the software elements at the functional level Where ap plicable specific ISDN standard documents such as CCITT Q 921 Q 931 and X 25 will be referenced rather than dupli cating the information here 2 2 HPC EXECUTIVE The HPC Executive provides a multitasking environment within which the ISDN and applications tasks can run and it provides various system services to those tasks The serv ices of the Executive are available to both tasks and inter rupt service routines 2 2 1 Tasks Priorities and the Ready Queue A task is a subroutine which can be run called by the Exec utive Tasks are managed by the Executive as Task Control Blocks TCB s A task s TCB contains all the parameters needed by the Exeuctive to handle the task in particular the task s priority and its current starting address Tasks which are not blocked waiting for a semaphore or for mail are considered to be ready to run and their TCB s are queued on the Ready Queue in the order of the tasks prior ities The Task Scheduler runs the task at the head of the Ready Queue i e the highest priority task that is ready to run In this way the processor is always given to the highest priority task that is ready to run Once a task is started it continues to run until it does a Semaphore Wait ReadMail or Return or until a higher pri ority task is put on the Ready Queue at which time the scheduler has the opportunity to once
36. pecific task tailored to the ca pabilities of the actual terminal equipment number of termi nals handsets etc 1 5 6 Management Entity Task The Management Entity Task which is only generically de fined in Q 921 and Q 931 handles housekeeping functions 1 0 Architectural Description Continued for all layers These functions include TEI negotiation with the network management entity and the handling of unre coverable errors This task implements as much of the man agement entity as is currently defined and in addition what ever is necessary for the operation of the other tasks 1 5 7 Tracer Task The Tracer Task serves two purposes to demonstrate the lower ISDN layers via a menu driven telephone emulation mode and to trace system mail message traffic 1 5 8 Task_View Task Exerciser and Debugger Task__View is a special purpose task that can be inserted into the multi tasking Executive environment in place of the Tracer Task It reads and interprets a user supplied ASCII scenario file Under control of this senario file Task__View sends mail messages to a specified mailbox or mailboxes where they are read by the task under test Mail messages sent by the task under test in response to this input are then displayed by Task__View In this way the task may be exer cised and debugged 2 0 Functional Description 2 1 INTRODUCTION This description defines the functional requirements of the ISDN Basic Rate
37. re configuration and application independent The Layer 2 Task provides both the USER SIDE and the NET WORK SIDE implementation of the CCITT Specification Q 921 The Layer 3 Task provides the USER SIDE imple mentation of CCITT Specification Q 931 The Layer 2 Task has been designed to use many of the same routines to implement the link access procedures on either the signaling D channel or the bearer B channel LAPD or LAPB Design decisions have also been made to facilitate the implementation of V 120 the rate adaption pro tocol that processes LAPD frames on a bearer B channel The Management Entity Task and the Call Control Task are Application Specific Tasks that are closely coupled to the specific system hardware configuration and the Central Of fice Network Entity Software These tasks are provided for demonstration purposes to drive the ISDN layer entities Ap plication users must either replace or extensively rewrite these tasks to match their particular ISDN Application envi ronment The System Utilities include the power up reset Main Task the NMI handler the Timer interrupt handler and the Watchdog Task The Tracer utility provides the capability of on line tracing of intertask mail messages and task states Tracer is primarily a passive task it displays messages that it receives from other tasks Tracer also provides a user interface for Tele phone Simulation The remainder of this document is dev
38. river task communication by means of mail messages which can be sent and picked up and semaphores which can be signaled and awaited Timers which are equivalent to mail messages with a specified delay and which allow tasks and drivers to time their activities and time out when an expected event does not occur Memory management to allocate and deallocate fixed size buffers as needed by tasks and drivers Application tasks and I O drivers developed by users of the HPC can easily be inserted in the HPC Executive environ ment and can take full advantage of its services 1 4 ISDN TELECOMMUNICATIONS STANDARDS 1 4 1 CCITT Standards The Layer 2 Task implements CCITT 1988 Blue Book specification Q 921 LAPD and Layer 2 LA B of CCITT specification x 25 The Layer 3 Task implements the Protocol Control Proce dures of CCITT 1988 Specification Q 931 The Layer 3 Task implements the circuit switched proce dures described in Section 5 The Layer 3 Task implements the Protocol Control procedures and some of the Resource Management The Call Control Task implements a demon stration version of the Call Control Procedures and the bal ance of the Resource Management In terms of the specification and description language SDL diagrams in the Q 931 specification the Layer 3 Task imple ments Figure 38 26 pages The establishment and release of logical links are fully cov ered in the Layer 2 specifications Q 921 but the Layer 3 asp
39. roviding error free in sequence transmis sion reception and multiplexing of messages received by an HDLC controller connected to the D signaling channel The event driven state machine architecture described above enables a single software module to support simulta neous activity on multiple logical connections The Layer 2 Task also supports X 25 LAPB processing for messages re ceived by a second HDLC controller connected to a bearer B channel 1 5 4 Layer 3 Task The Layer 3 Task implements the user side of the Protocol Control Procedures of Q 931 which are used to setup an swer suspend resume and disconnect a call Specifically it implements all of Figure 2 Q 931 of Q 931 The event driven state machine architecture described above en ables a single software module to support simultaneous ac tivity relating to calls on both bearer B channels 1 5 5 Demonstration Call Control Task The latest versions of Q 931 separate the Layer 3 proce dures into Protocol Control Procedures and Call Control Procedures Call Control Procedures are application depen dent These procedures handle bearer channel selection and actual establishment of the voice channel As Q 931 notes these procedures can also be considered to be part of the Applications Layer The Call Control Task implements a minimal subset of the Call Control Procedures for demon stration purposes In an actual application this task will be replaced by an application s
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41. stined for that task Mail is prioritized When a task calls upon the Executive to perform a SendMail it specifies the priority of the message which is inserted in the specified mailbox queue sorted by priority 2 2 6 Timers The Executive includes a timing facility specifically designed to handle the time outs typical of telecom protocols and oth er real time applications Timers are essentially a form of delayed mail When a task sets a timer the task provides a mailbox identifier a mail message and a time delay value When the specified time delay is up i e when the timer expires the mail message is mailed to the specified mailbox When a task sets a timer it receives a timer ID which can be used to cancel the timer if necessary before it expires 2 2 7 Memory Management The memory manager is responsible for allocating and deal locating fixed size memory blocks from fixed size pools which are completely defined at compile time A memory pool may reside in extended memory 2 2 8 System Module and Interface Module The Multi Tasking Executive Software is available either as source code or as object code The interface module which must be modified to insert application tasks is always sup plied as source code 2 3 1 O DEVICE DRIVERS I O Device Drivers serve as interface routines between the HPC hardware machinery and the HPC Executive and Appli cation Tasks Input operations data heading toward Ap
42. tomer product design Customers are responsible for their products and applications using TI components To minimize the risks associated with customer products and applications customers should provide adequate design and operating safeguards TI does not warrant or represent that any license either express or implied is granted under any TI patent right copyright mask work right or other TI intellectual property right relating to any combination machine or process in which TI products or services are used Information published by TI regarding third party products or services does not constitute a license from TI to use such products or services or a warranty or endorsement thereof Use of such information may require a license from a third party under the patents or other intellectual property of the third party or a license from TI under the patents or other intellectual property of TI Reproduction of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties conditions limitations and notices Reproduction of this information with alteration is an unfair and deceptive business practice TI is not responsible or liable for such altered documentation Information of third parties may be subject to additional restrictions Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service
43. wing main parts shown in overview in Figure 1 1 e HPC Executive providing an operating environment and services for the ISDN software and for additional applica tion software written by OEM users of the HPC e O Drivers interfacing to the DMA HDLC controllers on the HPC16400 and to the TP3420 S Interface Device e Data Link Layer Software implementing the CCITT Q 921 and X 25 link access procedures LAPD and LAPB e Network Layer Software implementing the Protocol Con trol Procedures defined in the CCITT Q 931 standard e Demonstration Call Control Module allowing a develop ment engineer at a terminal to make and receive ISDN phone calls which exercise the above software e Tracer Module allowing a development engineer at a ter minal to monitor the operation of the above software e 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 Intertask communications and the interface between tasks EP X R Eo CG u R J SCHEDULER MANAGER TA IM v TERMINAL ADAPTER TASK E X 3 AND X 25 or V 120 ST DA DEMONSTRATION CALL Fs CONTROL TASK TK we ws pe A LAYER 2 TASK AND RATE ADAPT SD ve ve Pi ped Cp y TV SERVICE 1 INTERRUPT SERVICE interRuPT SERVICE INTERRUPT wE J REQUEST HANDLER f REQUEST Hanpier REQUEST HANDLER a p HANDLER HANDLER HANDLER

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