At 14:36 -0600 11/20/04, Andrew, a Mac Freak wrote: > >Excuse my ignorance, but what's a scope and handshake lines?
Oh oh. . . "scope" is short for oscilliscope which is a form of voltmeter that shows a curve on a cathode ray tube. Think of is as a high speed plotter that plots voltage vs. time on a recurring basis. You probably need to learn about such things before messing very much with your Mac's serial ports. Mac serial is really RS422 which is a low voltage version of RS 232 that uses two wires for each signal. They are balanced with one wire going up in voltage and the other down. Apple chose the voltages so that - just barely - the ports can be connected to "standard" RS232 devices with simple wiring. Having said that Apple also provides two handshake lines similar to the CTS and DTR lines called out in the RS232 specifications. Those are not balanced. They are used for "clear to send" and "data terminal ready" indications which synchronize communications. On an oscilloscppe you will seem bouncing up and down while two devices are communicating. You will also use a scope to see the levels on the data lines as they send start, stop, and data bits. A buzzword is "LocalTalk". You can probably Google for a bunch of basic information on that. There are integrated circuit chips available that produce and receive the required signals. Motorola made some of them. If you find a datasheet it will contain a lot of the data you need. RS485 is another thing you might look up. It describes the use of Apple's serial ports as they are used for machine to machine connectivity using AppleTalk. The transmit and receive lines are connected to each other and software guarantees that two transmitters don't talk at the same time. There is a book, Macintosh Family Hardware Reference, Addison Wesley, 1988, ISBN -0-201-19255-1 which is probably out of print but it is just what you need. Deep down you need something simple to play with like, perhaps, a kit from Mouser or All Electronics. Just learning to 'scope the wires while talking to a modem would be instructive. -- --> On the eighth day, about 6 kiloyears ago, the Lord realized that free will would make man ask what existed before the Creation. So He installed a few gigayears of history complete with a big bang and a fossilized record of evolution. <-- -- Compact Macs is sponsored by <http://lowendmac.com/>. Support Low End Mac <http://lowendmac.com/lists/support.html> Compact Macs list info: <http://lowendmac.com/lists/compact.shtml> --> AOL users, remove "mailto:"; Send list messages to: <mailto:[EMAIL PROTECTED]> To unsubscribe, email: <mailto:[EMAIL PROTECTED]> For digest mode, email: <mailto:[EMAIL PROTECTED]> Subscription questions: <mailto:[EMAIL PROTECTED]> Archive:<http://www.mail-archive.com/compact.macs%40mail.maclaunch.com/> --------------------------------------------------------------- >The Think Different Store http://www.ThinkDifferentStore.com ---------------------------------------------------------------
