G.ABRAMS@SU-SCORE.ARPA (Info-Atari Moderator) (08/28/86)
Return-Path: <FGCBA10%BLEKUL11.BITNET@WISCVM.WISC.EDU> Received: from WISCVM.WISC.EDU by SU-SCORE.ARPA with TCP; Wed 27 Aug 86 06:39:49-PDT Received: from (FGCBA10)BLEKUL11.BITNET by WISCVM.WISC.EDU on 08/27/86 at 03:42:54 CDT Date: Wed, 27 Aug 86 10:42:23 SET To: info-atari16-request@su-score.ARPA From: FGCBA10%BLEKUL11.BITNET@WISCVM.WISC.EDU Subject: re: 520ST parallel printer port doubles characters? DEER JAN, THE PROBLEM OF THE DDOOUUBBLLEEDD CHARACTERS LIES IN THE STROBE PIN NUMBER 1 THAT GOES TO THE PRINTER. THE PULSE IS TO LONG SO AFTER THAT THE BUSY-LINE HAS DROPPED THERE IS STILL A STROBE PULSE AND THE CHARACTER WILL BE PRINTED AGAIN. ______ STROBE ---------I I--------------- I I I-----------------I I------------I I I BUSY-------------I I------------------- INTERUPT THE STROBE LINE AND PUT THE FOLLOWING SCHEME BETWEEN IT THEN THE PROBLEM HAS TO BE SOLVED. I +5V I R = 10K I I 2.2NF I--II--I +5VI I I I I I I---.----.------.-----.----.----.----.----.----I I 16 9 I I 74LS123 I I 1 8 I I---.----.------.-----.----.----.----.----.----I I I I I I I I------I I I I I I I I +5V I ----- R = 100 I GND I I I I I I STROBE IN STROBE OUT FROM COMPUTER TO PRINTER -------