Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site sdcsvax.UUCP Path: utzoo!linus!philabs!sdcsvax!brian From: brian@sdcsvax.UUCP (Brian Kantor) Newsgroups: net.micro,net.micro.atari Subject: Re:Centronix interface Message-ID: <3736@sdcsvax.UUCP> Date: Sat, 3-Sep-83 09:19:11 EDT Article-I.D.: sdcsvax.3736 Posted: Sat Sep 3 09:19:11 1983 Date-Received: Sun, 4-Sep-83 01:03:31 EDT References: <400@houxn.UUCP> Organization: U.C. San Diego, CS Dept Lines: 66 The "Centronics Standard Interface" refers to the connector and signals sent to the printer and expected from the printer; in the case of the connector it specifies only the PRINTER end of the cable, and not the computer end of the printer cable. The printer cable is expected to be 12 pair cable, each pair twisted, and can be shielded overall to reduce interference with radio/tv. The connector on the printer end is an Amphenol #57-40360 36pin male connector with hood. The signals and pinouts are as follows: Signal Ground pin pin Signal name Remarks ------ ------ -------------- ----------------------- 1 19 Data Strobe/ paired with ground 2 20 data bit 0 ditto 3 21 data bit 1 ditto 4 22 data bit 2 ditto 5 23 data bit 3 ditto 6 24 data bit 4 ditto 7 25 data bit 5 ditto 8 26 data bit 6 ditto 9 27 data bit 7 ditto 10 28 Acknowledge/ ditto 11 29 Busy ditto 12 Paper Out paired with 13 13 Printer On Line paired with 12 17 Chassis Ground (cable shield) How it works: (All signals are TTL levels; high refers to ttl high output voltage, 2.4 volts minimum; low is TTL low, less than .8 volt. Printer represents one standard TTL load maximum.) The data is placed on the parallel data lines pins 2 thru 9, then at least 500 nS later, the STROBE/ line (normally high) is taken low for at least .5 uS, and for no longer than 500 uS. 500nS later the data may change if desired. Within 2 uS the BUSY line will go high if the operation requested causes the printer to become busy. After the printer completes whatever operation was requested (printing, paper movement, etc) the BUSY line will return to its low state. A low pulse on the ACKNOWEDGE/ (normally high) line will then occur. At this point the sequence can be started over again to send the next character or command. If the printer runs out of paper, or is taken off-line, the BUSY line will go high, and the appropriate line (PAPER OUT or ON LINE) will indicate the status. Most computer systems check these after the BUSY line has been continuously high for 1 second or more, and print a message telling the operator to correct the printer fault. Taken from centronics document "Technical Manual for Model 101A Printer" Appendix B, July 1975. (A note: in many cases, the driving microcomputer is slow enough that it is only necessary to check the BUSY line, and the ACK/ signal may be ignored.) -- Brian Kantor, UCSD. {philabs,ucbvax} !sdcsvax!brian sdcsvax!brian@nosc