Raytheon DIDS-400 Series Technical Manual page 178

DIDS -402 -2AM 13
4-24 TIMING AND DISCRETE BOARD A14
Circuits contained on the timing and discrete board (Raytheon Drawing
No. 407905) produce timing pulses for controlling data transfers and all other
internal logical operations performed by the Display Terminal. All interface
circuits are also contained on A14. These circuits provide MIL-STD-188B inter-
'face levels for transferring data or status to and from the connected CPU 1/0
device. The timing circuits contained on A14 are:
Master Oscillator
Minor Vertical Sweep
Phase Counter
Bit Counter
Eight-Character Counter
Character Counter
Line Counter
l200-Baud Circuitry
lO-Bit Decimal Counter
Miscellaneous Circuits
Cursor Video
Blanking
The interface circuits contained on Al4 are:
Request-to-Send Transmitter
Transmitted Data Transmitter
Clear-to-Send Receiver
Received Data Receiver
4-24. I Master Oscillator
The master oscillator is shown schematically in Raytheon Drawing
No. 407905 Transistor Ql4 is connected in a modified Colpitts configuration and
produces low-level oscillations of 2.4576 MHz which are limited and coupled
to the base of Q15. Q15 is a saturated switch that limits the oscillator output to
position excursions of the signal. The oscillator signal output is distributed to
three points: the minor vertical clock input, the phase counter clock input, and
the input of the phase counter decodes.
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