Re: ATN questions on the serial bus

From: Greg King (
Date: 2003-06-10 12:40:40

-----Original Message-----
From: Baltissen, R (Ruud)
Date: Saturday, June 07, 2003, 03:13 AM
> Hallo Marko,
> > I remember seeing a piece of code that tells a printer to
> > LISTEN and a disk drive to TALK, in order to print a file
> > while the computer could do something else.
> Quite simple if two drives are concerned:
> -- you tell the TALKER what file to send
> -- you tell the LISTENER what file to receive
> -- you tell the LISTENER to start to LISTEN
> -- you tell the TALKER to start to talk

A fifth step is needed:
-- you "disconnect" from the bus.

The General Purpose Instrument Bus allows multiple controllers.  They (and
other devices) have three modes:  listen, talk, and idle.  But, Commodore's
version allows only one controller (the computer); it never idles!  That
program "fakes" the idle-mode.  It sets the IEC's output-buffers so that
they let the lines float (high).  That step stops the computer from
interfering with the transfer between those devices.

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