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Method for Asynchronously Handling Data Using PC Interrupt Vectors

IP.com Disclosure Number: IPCOM000034165D
Original Publication Date: 1989-Jan-01
Included in the Prior Art Database: 2005-Jan-26
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Duffield, DM: AUTHOR [+3]

Abstract

To handle displaying incoming asynchronous data on an IBM PC (personal computer), the end-user application must be temporarily interrupted from doing work while the incoming data is received and displayed while at the same time minimizing the use of resident memory. This method accomplishes this purpose. In the case of PC Support/36, a message which has been received is being displayed to the user and will continue to be displayed until the user chooses to continue with the application. In order to receive and display data using the method described in the preceding article, the DOS function calls (interrupt 21H), BIOS keyboard I/O (16H) and BIOS timer (08H) are hooked, thus temporarily interrupting the running of the PC application.

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Method for Asynchronously Handling Data Using PC Interrupt Vectors

To handle displaying incoming asynchronous data on an IBM PC (personal computer), the end-user application must be temporarily interrupted from doing work while the incoming data is received and displayed while at the same time minimizing the use of resident memory. This method accomplishes this purpose. In the case of PC Support/36, a message which has been received is being displayed to the user and will continue to be displayed until the user chooses to continue with the application. In order to receive and display data using the method described in the preceding article, the DOS function calls (interrupt 21H), BIOS keyboard I/O (16H) and BIOS timer (08H) are hooked, thus temporarily interrupting the running of the PC application. The interrupt cannot be allowed to occur until the data has been responded to by the send user. Most applications running on DOS use the DOS function call interrupt to perform work. Prior to being able to receive asynchronous data, a "poll rate" needs to be established. This is done via the MMRI entry in a configuration file set up by the user. When the command to load the program as a resident extension of DOS executes, it reads this file for the number of seconds to use as the "poll rate". By hooking interrupt 08H (BIOS Timer), the program can determine when it is time to "poll" the PC Support/36 Router to check if any asynchronous data has been received. The "poll" takes place on the next DOS function call or next BIOS keyboard I/O (which is done by DOS at the prompt line or when an application uses DOS to get the next keystroke) and the timer has indicated that the next interval of time has expired. Once the data has been...