Printronix T3204 Maintenance Manual page 94

The resistor R120 sets the operating current for the label present sensor emitter
(LED). The resistor R80 with R81 are the load resistors for the label present sensor
detector (photo transistor). Diodes D2 and D3 serve as voltage limiting diodes and
capacitors C65 and C81 serve as AC coupling capacitors.
Interfaces
1. Paper Cutter
The printer has provisions for an optional paper cutter that attaches to the
front of the unit. The paper cutter board connects to 8-pin connector, J8. A
cutter output signal, J8–3 is generated by the i960 via the latch U2–13 and
transistor switch Q3. A cutter input signal, J8–4, is available as data bit 10 at
data status buffer, U14. Unregulated +24 volts is provided to the optional
cutter board at J8–2 where motor control and connection to the cutter is
accomplished. The voltage output is fused with a fast blow 1.5A fuse (F4)
and is regulated down to 5V on the cutter board.
2. Ribbon Saver
Connection to the optional ribbon saver board is provided by the 8-position
connector, J9. Two inputs, J9–3 and 4, are available to the i960 as data bits
13 and 14 at data status buffer, U14. Two outputs, J9–1 and 2, are generated
by latches U2–18 and 19. These latches are activated by the i960 executing
a store operation to latch U2 using data bits 0 and 1. Unregulated fused +24
volts is available through F5 at J9–7 to the ribbon saver board where
appropriate control is accomplished.
3. General Purpose
A 7-pin circular DIN connector, J14 provides the following signals for external use.
J14 – 1
J14 – 2
J14 – 3
J14 – 4 & 6
J14 – 5
J14 – 7
Real Time Clock
The Real Time Clock (RTC) chip U1 is used for time keeping purposes as
well as non-volatile data storage. The RTC is a self-contained subsystem that
includes a lithium battery, quartz oscillator and support circuitry. The RTC has
64 RAM locations (bytes). Fourteen bytes are used for clock and control
registers and 50 bytes are available as general purpose RAM.
The signal coming out on U1–23 is a square wave with a frequency equal to
1024 Hz. This signal is divided by 8 inside U54. The signal exits U54–30 as
an 8 Msec clock going to the i8960JA (U47–B12).
8–10
Ground
Cutter out signal (same as J8–3)
Fused unregulated +24 volts (same as J9–7)
Input signals available as data bits 14 and 15 at data buffer U13.
Output signal from transistor switch Q4 and latch U46–13.
Fused and unregulated +9 volts.
Circuit Description