HP 13255 Technical Information page 33

13255
Cartridge Tape Module
13255-91032/31
Rev AUG-01-76
3.1.10.2 When a cartridge is inserted in Unit 1, the el line is pulled low caus-
ing U17, pin 8 to go high. This allows e3 to charge through R2 and R3.
After approximately 1/2 second, Q2 turns on and pulls U13, Pin 1 low
causing CINt to go high and indicating the presence of a cartridge.
U13 is a Schmitt gate used to provide hysteresis so that the slow fall
time of the collector 02 wIll not cause oscillations at the output of
U13.
when the cartridge is ejected trom Unit 1, all actions of the signals
are inverted with the exception of capacitor C3 which discharges only
through R2 (C3 discharges 464 times faster than it charqes when a car-
tridge is inserted). The analysis for unit 0 cartridge insertion and
ejection are similar, except that U17, Pin 10, Rl, RSO, Cl, Qt, and
U13, Pin 10 are involved In affecting the state of CINO.
3.2 fUNCTIUNAL DESCRIPTION - CARTRIDGE ELECTRONICS peA. Refer to the block
diagram (figure 7), sch~matic diagram (figure 8), component location
diagram (figure 9), and parts lists (02640-60034 and 02640-60066)
located in the appendix.
The Cartridge Electronics PCA is a small peA (part Of the head bridge
assembly of the CTU Transport) mounted to the tape meChanism's head
mount. This assembly includes a 14-conductor ribbon cable Which Plugs
into the Read/Write PCA. The ribbon cable provides all the electrIcal
connections required
by
the mechanism, except motor current.
3.2.1 CI SWITCH - CARTRIDGE ELECTRONICS peA.
3.2.1.1 The cartridge Inserted (eI) switch (S2) is activated by the presence
of a cartridge in the mechanism. The information concerning the
presence or absence of a cartridge is transferred to the firmware,
which takes the appropriate action.
3.2.1.2 When a cartridge is inserted, contact is made between two pads on the
Cartridge Electronics PCA. This action connects the Cl line to ground.
When a cartridge is not inserted, the Cl line is pulled to +5 volts
by
a resistor on the Read/Write PCA. No "debouncing" circuitry is re-
quired Since a delay Is provided by circuitry on the Read/write peA.