palmer@cit-vax.Caltech.Edu (David Palmer) (11/05/86)
Organization : California Institute of Technology Keywords: serial, audio I would like to use the serial port with an external clock for some hardware I am making. (An audio digitizer running at ~400 kbaud. The final cost should be under $20. I will post the plans to the net if anyone is interested after I have finished it.) The serial driver section in my copy of Inside Macintosh (Phone book version) does not tell me how to use the external clock, nor does it tell me how to change the clocking frequency from whatever it usually is (16 times the baud rate, I think) to equal the baud rate. I remember that when the Mac came out the "virtual slot" concept gave a maximum data rate of ~1 Mbaud with external clocking, ~400 kbaud with internal clocking, but IM does not tell us how. David Palmer palmer@cit-vax.edu ...seismo!cit-vax!palmer I've followed you, talked to your neighbours, tapped your phone, and even shot at you to see how you would react. From my observations I have come to one irrefutable conclusion: You are Paranoid.
dgold@apple.UUCP (David Goldsmith) (11/06/86)
In article <1120@cit-vax.Caltech.Edu> palmer@cit-vax.UUCP (David Palmer) writes: >... >I would like to use the serial port with an external clock for some hardware >I am making... >The serial driver section in my copy of Inside Macintosh (Phone book version) >does not tell me how to use the external clock, nor does it tell me how >to change the clocking frequency from whatever it usually is (16 times >the baud rate, I think) to equal the baud rate. The serial driver only supports asynchronous communications at one of a fixed set of baud rates. In order to communicate at 400KB, you will need to use one of the synchronous communication modes of the Z8530 SCC hardware in the Mac (documented in the hardware chapter). You will have to write your own driver software to accomplish this, and access the hardware directly. In addition to Inside Mac, you will need the Z8530 technical reference, available from the manufacturer. Although the Z8530 supports a large number of communications modes (async, bisync, HDLC, SDLC, etc), the serial driver was only intended to support standard async, not any of the fancier stuff. I'm not sure the Z8530 even supports async above 56KB. AppleTalk uses one of the synchronous modes and has its own low-level device driver. -- David Goldsmith Apple Computer, Inc. MacApp Group AppleLink: GOLDSMITH1 UUCP: {nsc,dual,sun,voder,ucbvax!mtxinu}!apple!dgold CSNET: dgold@apple.CSNET, dgold%apple@CSNET-RELAY