ADC Home > Reference Library > Technical Notes > Legacy Documents > Hardware & Drivers >

Legacy Documentclose button

Important: This document is part of the Legacy section of the ADC Reference Library. This information should not be used for new development.

Current information on this Reference Library topic can be found here:

VIA IC Q&As

CONTENTS

This Technical Note contains a collection of archived Q&As relating to a specific topic--questions sent the Developer Support Center (DSC) along with answers from the DSC engineers. Current Q&A's can be found on the Macintosh Technical Q&A's web site.

[Oct 01 1990]


Use Time Manager instead of VIA2 timer T1

Date Written: 11/27/91

Last reviewed: 11/27/91

The Apple Macintosh Family Hardware Reference, first edition, (page 17-28) says VIA2 timer T1 can generate interrupts up to every 1.2766 microsecond. Is there any documentation for programming the timer to generate the interrupt at high speeds and installing the interrupt service routine? By the way, the Time Manager documented in Inside Macintosh Volume IV (page 299) is capable of generating interrupts at the accuracy of only one millisecond.

Apple discourages direct use of the VIA2 because it's not present on all Macintosh CPUs. It's absent on the popular Macintosh IIci and IIfx models, for example.

Contrary to the outdated Inside Macintosh Volume IV Time Manager documentation, the Time Manager in System 6.0.3 and later has accuracy on the order of 1 microsecond. See Inside Macintosh Volume VI for details on new Time Manager features.

Back to top

Downloadables

Acrobat gif

Acrobat version of this Note (40K)

Download

Back to top

Did this document help you?
Yes: Tell us what works for you.
It’s good, but: Report typos, inaccuracies, and so forth.
It wasn’t helpful: Tell us what would have helped.