TAPE TRANSPORT CONTROL

The circuit boards in the control section of the card cage control the tape transport by generating internal tape transport commands which are based upon com- . mands from the interface, as well as status Signals from the tape transport.

In the Model 9100, the following circuit boards control the tape transport:

Type 3841 Line Terminator Type 3842 Interface Control Type 3843 Pushbutton Control Type 5719 Sensor Amplifier/Driver Type 6667 Sequence Control

Type 5733 Ramp Generator Type 6666 Servo Control

Figure 3-1 is a block diagram of the Model 9100.

Tape commands from the interface connector are supplied to the interface control board which will generate internal tape transport commands if certain interlocks are satisfied. These tape transport eom-mands are then supplied to the Pushbutton Control board. The Sequence Control and the Pushbutton Control also contain several interlocks which must be satisfied before the Pushbutton Control can encode the tape motion commands onto one of three command lines: RUN NORMAL (RNNl), RUN FAST (RNF1), and REVERSE SELECT (RVSl). These three com-mand lines are supplied to the Ramp Generator, which provides linear ramp-up to speed and linear ramp-down to standstill in order to minimize tape stress and maintain accurate tape speeds. The out-put of the Ramp Generator is supplied to the capstan ^I servo preamplifier on the Type 5666 Servo Pream-plifier board. The capstan servo uses the Ramp Generator output to control capstan motor current, while the capstan tachometer supplies a stabilizing feedback voltage to the capstan servo based on cap-stan motor speed.

The Type 5719 Sensor Amplifier / Driver receives input from the file protect switch, load point sensor, and end of tape sensor. These signals are amplified and gated, then supplied to the Pushbutton Control and Sequence Control as tape transport status signals for controlling their interlocks.

The Type 3844 Sensor Amplifier/Driver module also contains the drivers for the WRITE, READ, and SELECT indicators on the main control panel.

3.2.1 SEQUENCE CONTROL

Due to certain special sequencing requirements in-volved in controlling the tape transport, a speCial Sequence Control module has been developed for the Model 9100. Transport control pushbuttons on the maIn control panel connect directly to this board.

In addition, broken tape, vacuum switch, and load point status Signals are input to the Sequence Control board. Thus, when tape breaks or vacuum pressure drops, "the Sequence Control will initiate the appro-priate tape transport command to stop reel movement.

Also, the sequencer will condition the actions caused by pressing the REWIND pushbutton dependent upon whether tape is in front of or past the load point marker.

Four sequences are discussed: the POWER ON se-quence, which occurs after the POWER pushbutton is pressed, the LOAD sequence, which follows the POWER ON sequence after the LOAD pushbutton is pressed, the UNLOAD sequence, which occurs when REWIND command is given and the tape is on the load point marker, and the POWER OFF sequence, when unit is loaded and power is turned off from the front panel.

3.2.1.1 POWER ON Sequence

When the POWER pushbutton is pressed, the low power transformer and various regulated voltages are generated. The vacuum blower and high power transformer are enabled through main relay K4.

3.2.1.2 LOAD Sequence

During this sequence, the vacuum blower motor is turned on, +24 vdc and -24 vdc is supplied to the electronics, servo relay Kl is actuated to enable reel motors and power latch, tape is tensioned and

306-9100-200A

Figure 3-1. Control Logic Block Diagram

306-9100-300A

L ___________________ J

Figure 3-1.' Control Logic Block Diagram

drawn into the vacuum columns, and the reel servo loop is closed. At the completion of this sequence, the tape is properly tensioned. The capstan servo now receives the command to advance at normal speed to load point and then stops. If load point is not reached within 6 seconds after pressing the LOAD pushbutton, the sequencer will command the trans-port to rewind the tape, searching for load point.

All operation is interrupted in case of broken tape or loss of vacuum as determined by the vacuum switch.

In this instance BROKEN TAPE true signal will be supplied from the Sequence Control and all servos will be disabled immediately. An END OF TAPE true signal from the END OF TAPE sensor will not terminate a write operation. Instead, an EOT status is given to the interface, which should be used to generate a proper sequence to terminate writing., 3.2.1.3 UNLOAD Sequence

During an unload operation, the tape is slowly and completely rewound onto the supply reel after it stops at load point during a normal rewind sequence.

To initiate the unload operation, the transport must be taken off line, either through an OFF LINE inter-face command or by pressing the ON LINE push-button. Next the REWIND pushbutton is pressed.

This sets the unload flip-flop on the Sequence Con-trol board, causing UNLOAD true to be output.

This connects the supply reel motor to -8 vdc

Note that the POWER pushbutton is disabled during the entire unload operation.

3.2.1.4 POWER OFF Sequence

When the POWER switch is shut off, the vacuum motor turns off immediately. The sequence is: vacuum switch off, sensor disable true (enabling the reels to remove tape from the vacuum chamber), servo dis-able true (applying braking signals to reels), all power then turned off.