HP E42 manual 69.A3 Oscillator Support, Decade Counting Assembly DCA

Model 5328A

Theory of Operation

4-64.Display Control

4-65.The display control section on Al Motherboard acts as an interface between the A16 Display board and the other circuits of the counter.

4-66.The outputs of the A16 Display Board FUNCTION and RESOLUTION switches go to the ROM (A1U37). The outputs of the ROM position the decimal point and annunciators in the dis- play and provide control functions for other circuits of the counter. Data from the data bus is translated from BCD to seven-segment form in decoder U41 and sent to the display which is strobed by U39. U39 decodes the digit address code from BCD to one of 10 forms. Leading zero blanking is provided by the latch comprised of U32B and U40B. Latches U25, U26, U27, and U31 provide outputs related to function and time base codes for use in other sections of the instrument.

4-67.State Control

4-68.The state control section is comprised of circuits U1, U2, U3, U4, and US. Decade Counter U1 generates the digit select strobe code for the display. Circuit U4 receives the Sample Rate signal and generates the main Reset, Transfer, and Inhibit signals.

4-69.A3 OSCILLATOR SUPPORT

4-70.An oven-temperature-regulated crystal oscillator (A3A1) supplies the precision 10 MHz time base signal in the 5328A. The A3A1 crystal oscillator (also designated HP Model 10544A) is in rectangular metal enclosure which plugs into the A3 Oscillator Support. The A3 Oscillator Support in turn plugs in the A1 Motherboard.

4-71. A3 Oscillator Support

4-72.On the A3 Oscillator Support five separate functional circuits are provided: a voltage regulator, an external signal detector, and amplifier-multiplier, a multiplexer, and a 10:1 divider. Integrated circuit U3 is a voltage regulator which regulates the 25-volt power at about 13 volts for the oscillator. External signal detector U4C will detect if an external signal (1, 5, or 10 MHz) is applied to the 5328A rear panel EXT OSC IN connector and send a signal, U4C(13), to control the U2 multiplexer. If an external oscillator signal is applied, the multiplexer selects the external signal for the 5328A time base. If only the A3A1 10 MHz signal is available, it is used for the time base. U4A and B produce a 10 MHz output, U4B(5), with either 1, 5, or 10 MHz input. The A3A1 10 MHz is divided to 1 MHz by U1 for the rear panel 1 MHz OUT connector.

NOTE

The rear panel 10 MHz OUT and 1 MHz OUT are both always derived from the 10544A, A3A1 Oscillator.

4-73.A3A1 Oscillator (HP 10544A)

4-74.The oscillator specifications are given in Table 7-3.This oscillator is a factory-serviced assembly. No circuit description is given here.

4-75.DECADE COUNTING ASSEMBLY (DCA)

4-76.The 5328A DCA is comprised of Decade Counter/Latches (U10 and U12) on the A1 Motherboard and U1A, U3, and U4B on A4 Function Selector Board, The Motherboard contains output enable circuitry (U6, U7, and U9) for controlling the counters output data, signal over- flow indication, and circuitry for strobing data into the display (U41). The data output of each Decade Counter in the DCA corresponds to a digit on the display. The first Decade Counter in the sequence of operation corresponds ‘to the least-significant-digit and the last to the most- significant-digit. Digits 0 through 5 are processed by U12, digit 6 by U10, and digit 7 by U11.

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