Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!sdd.hp.com!spool.mu.edu!munnari.oz.au!diemen!tasman!steveh From: steveh@tasman.cc.utas.edu.au (Steven Howell) Newsgroups: comp.sys.mac.hardware Subject: ADB Transmitting speeds. Message-ID: Date: 24 Apr 91 06:07:58 GMT Article-I.D.: tasman.steveh.672473278 Sender: news@diemen.utas.edu.au Distribution: comp Lines: 27 Evening folks. I have been conducting experiments with the ADB, in an effort to design various add on devices. To date i have figured out that it operates using PCM and standard digital comms. I know it issues a sequences of commands to initalize each of the sixteen possible devices, and then drops into a clock reference mode, waiting to receive data. When a key is press,the data is dropped onto the line, and when a key is released keyup data also drops on the line, thus detecting the duration of time a key was pressed for. But the data used for that key press seems to have the same duration of time, but diffrent density, as if it was a PCM code. Each key has a diffrent tone, but so quick making it hard to see What i would like to know is what is the sample reference speed for reading data. I know the keyboard MPU is clocked along at 6.0MHz, but is this signal internally divided. I thought 500Hz to about 800Hz would be ample. Anyone have any idea's! thanks in advance. steveh .