HP 13255 Technical Information

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132!)5Cartridye Tape MOdule 13255-91032/24Rev AUG-01-76presence of gap (absence of flux transitions) on the tape. Tn addi-tion, this PCA contains the servo electronics for controlling tapemotion and speed for either CTU Transport. Analysis of the peA indi-cates that much of the circuitry is common for servo control ~nd readlwrite operations. The routing Of signals is accomplished for eachdrive by the read select switch, the unit function decoder, the ampli-fier select logic, and the tachometer feedback select and conditioninqcircuits. (Refer to the block diagram In figure 4.)3.1.1 UNIT FUNCTION DECODF.k - R~AD/WRITE PCA.3.1.1.1 The unit function decoder (U3) 1s a 1-of-10 decoder which determineswhether the Read/write peA is in Read or Write mode. It also deter-mines the CTU Transport from which flux transitions are received, orto which flux transitions are sent.3.1.1.2 When RE and line usa are low, yO and Ql are active outputs and Head 1is driven by DATA as shown In the truth taole below. When RE is low,and USO is high, Q2 and Q3 are active outputs and Head 0 Is drven byDATA as shown below.1 - Of - 10 Decoder (U3)Truth Table=====================================================INPUTS OUTPUTSRE USO DATA 00 01 02 03 04 05 06 Q7~~------~~~~~-~-~~~~~-~-----~-~--~~-----~-~---~~--~~---------------------------------------------------------------- -----_ ...IL L LI IL HI H H H H H HIL L HI IH LI H H H H H H-----_ ... _.- -_._--- -------IL H LI H H IL HI H H H HIL H lil H H tH LI H H H H----------- --_ ...... -------IH L LI H H H H IL HI H HIH L HI H H H H IH LI H H----------- -----.,. ----.--IH H LI H H H H H H IL HIIH H HI H H H H H H I H LI----------- ---------~--~~-~-~-~----~~~-------~-------~--~-~-~----~-~-~---------~-~-----------------~--~-~~~---~---~---------