Browse Prior Art Database

Timer Auto Load

IP.com Disclosure Number: IPCOM000087978D
Original Publication Date: 1977-Apr-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Bourke, DG: AUTHOR [+2]

Abstract

Program control of a wide range of timer-interrupting intervals is provided for a data processing system.

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Timer Auto Load

Program control of a wide range of timer-interrupting intervals is provided for a data processing system.

Preferably, the feature exists in conjunction with a timer attachment for a central processing unit (CPU). The attachment presents a logical interface to a controlling program.

Referring to Fig. 1, a timer 1 capable of counting modulo 2 EXP N maximum, where N equals the number of stages in the timer, is caused to count by gating an input clock signal on line 2 with a program controlled run signal on line 3 through And circuit 4. The clock has a period of Tc (Fig. 2). This timer is a presettable counter.

When timer 1 is not running, it may be loaded to an initial value IV by the CPU program via circuits 8 and 9. This loading is via an Auto Load Register 6, also of N stages. Both timer 1 and register 6 are loaded with the same initial value. Also, when timer 1 is not running, the program can enable or disable the Auto Load mode by line 10.

When caused to run by the program, timer 1 will generate carries every time it reaches its maximum value. The carries are sent to the program as interrupts with known time intervals. The program can use these interrupts to record time of day, schedule tasks, etc. This usage of timers is now practiced in the industry.

The apparatus supplies an extremely wide range of interrupting time intervals by allowing the program to select the timer's initial value, counting modulus, and Auto Load mode. Refer to Fig. 2. As...