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Asynchronous Task Scheduling

IP.com Disclosure Number: IPCOM000059980D
Original Publication Date: 1986-Feb-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 3 page(s) / 50K

Publishing Venue

IBM

Related People

Spagnol, V: AUTHOR

Abstract

Due to the growing complexity of communication networks, modems now include many functions such as line monitoring, network diagnosis and operator panel support. The software of the modems is generally comprised of the Interrupt Program and the Main Program. The function of the Interrupt Program is, at every baud, to write transmit signal samples to the line interface and to read received signal samples from the line interface. The Main Program is comprised of tasks according to the functions to be performed. Depending on the modem state the different tasks can be active or not, and a Scheduler Program controls the sequencing of the active tasks at the right time in a given modem state. The tasks are classified as synchronous or asynchronous.

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Asynchronous Task Scheduling

Due to the growing complexity of communication networks, modems now include many functions such as line monitoring, network diagnosis and operator panel support. The software of the modems is generally comprised of the Interrupt Program and the Main Program. The function of the Interrupt Program is, at every baud, to write transmit signal samples to the line interface and to read received signal samples from the line interface. The Main Program is comprised of tasks according to the functions to be performed. Depending on the modem state the different tasks can be active or not, and a Scheduler Program controls the sequencing of the active tasks at the right time in a given modem state. The tasks are classified as synchronous or asynchronous. They are synchronous when they must be executed once a baud time, such as the tasks related to signal processing. Conversely, asynchronous tasks are not related to the baud time. An asynchronous task may be executed from once every n bauds, to several times a baud. As shown on Fig. 1, the Scheduler Program is divided into two levels of scheduling determining priority between the different types of tasks. First, a General Scheduler looks at any request which is received. If at least a synchronous task is to be executed, the control is given to the Synchronous Scheduler. If no synchronous request is present, the control is given to the Asynchronous Scheduler. The asynchronous Scheduler is comprised of State Tables, one per modem state, where each entry is a "transfer control" to an Asynchronous Executable Module (XAEM). When the Asynchronous Scheduler is given the control, it addresses the current table entry by means of a pointer AEMADDR which, at any time, is updated with the next table entry address. Table organization As shown in Fig. 2, each State Table corresponding to each modem state three sections C1, C2, and C3 each of which includes a number of Asynchronous Executable Modules (AEM) having the same priority. For example, the AEMs of high priority section C1 have to be executed at least every 8 bauds, t...