Page 249 of Network Access & Connectivity Product Line by Patton Electronics

network access connectivity technical reference catalog 249 parallel ieee-1284 interfaces standard parallel both the 36-pin centronics® and db-25 connectors are commonly used for computer-to-printer communication the two physical variations are electrically compatible with one another so that only a special cable is required to allow them to operate with each other printer can communicate vital feedback to the host out of paper buffer full etc is to raise or lower a control pin the ieee-1284 standard outlines methods by which a printer can receive data from a host forward channel and communicate data back to the host reverse channel not just raise or lower control pins the two primary ieee-1284 modes the ones used by patton hardware are compatible and nibble compatible mode is the baseline and is simply forward channel parallel communication as implemented in the classic 36-pin centronics® format nibble mode is reverse channel communication using the four status lines of the parallel interface here s how nibble mode works data is sent from the printer to the host under the control of the host since only four lines are used instead of the eight commonly required for parallel data the byte is segmented into two 4-bit pieces and sent sequentially down the line the byte therefore becomes two nibbles ieee-1284 bi-directional parallel standard parallel communication sends data in parallel in one direction so a host can send data to a printer but the printer cannot send data back to the host the only way the centronics parallel interface primary ieee-1284 modes db-25 pin 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 db-36 pin 1 2 3 4 5 6 7 8 9 10 11 12 13 14 32 31 36 19 20 21 22 23 24 25 26 27 29 28 30 compatible mode nstrobe data 1 least significant bit data 2 data 3 data 4 data 5 data 6 data 7 data 8 most significant bit nack busy perror select nautofd nfault ninit nselectin signal ground nstrobe sg data 1 2 sg data 3 4 sg data 5 6 sg data 7 8 sg busy nfault sg perror select and nack sg nautofd nselectin ninit nibble mode hostclk signal/voltage source printer common common printer common printer printer printer printer computer computer computer computer computer computer computer computer computer signal designations 5 volts 18 chasis ground 17 logic ground 16 oscxt 15 supply ground 14 select 13 paper end 12 busy 11 acknowledge 10 data bit 8 9 data bit 7 8 data bit 6 7 data bit 5 6 data bit 4 5 data bit 3 4 data bit 2 3 data bit 1 2 data strobe 1 signal designations 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 undefined undefined undefined undefined fault input prime r input prime r busy r acknowledge r data bit 8 r data bit 7 r data bit 6 r data bit 5 r data bit 4 r data bit 3 r data bit 2 r data bit 1 r data strobe signal/voltage source printer computer common common common common common common common common common common common common ptrclk ptrbusy actdatareq xflag hostbusy ndataavail ninit 1284 active ibm pc style parallel interface signal/voltage source signal designations 25 24 23 22 21 20 19 18 17 16 15 14 signal/voltage signal designations source 13 select active high printer 12 paper end active high printer 11 busy active high printer 10 acknowledge active low printer 9 data bit 8 mse computer 8 data bit 7 computer 7 data bit 6 computer 6 data bit 5 computer 5 data bit 4 computer 4 data bit 3 computer 3 data bit 2 computer data bit 1 lsb computer data strobe active low computer common return ground common return ground common return ground common return ground common return ground common return ground common return ground common return ground computer select input active low computer initialize printer pimer active low printer error fault active low computer auto line feed active low not defined on the db-36 connector pins 15 33 34 35 visit us online www.patton.com fast delivery from your authorized distributor!

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