A19 Interface B Assembly 05340-60032 (Part Of Option 011) - HP 5340A Operating And Service Manual

4-207. The sample rate circuitry consists of A19Q1, AlSUlA, A19U2E, R1, and R2. R1 and R2
are located off of the pc board on the main chassis. The sample rate circuitry determines the
length of waiting time between measurements. At the end of a measurement, XAlgPlA(4) goes
low, allowing A19C1 to be charged through
the rate of charge on A19C1. When A19C1 charges sufficiently, Q1 conducts to trigger Schmitt
trigger U1A. When U1A triggers, U2E(ll) goes low and XAlgPlA(6) goes high.
4-208. Schmitt trigger U1B generates a reset when the RANGE and RESOLUTION switches are
changed or when RESET pushbutton S2 is pushed. When power is first turned on, reset is main-
tained a s C5 charges, allowing all circuits to stabilize.
4-209. U6D and U6C are buffers for the inhibit signal. The inhibit signal is low for the phase
lock mode and high for the direct count mode. U6B and U6A provide RANGE switch information
to A21 and A22.
4-210. Digit
Counter U4 keeps track of the counted data while
display. U3C outputs a low
4-211. For measurements using the phase lock loops, it is necessary to subtract 20 MHz from the
counted number to compensate for the 20 MHz phase lock loop
tracting a "2" from the appropriate column, as determined by the setting of the RESOLUTION
switch. U7 is 5-bit comparator that determines the proper time to subtract a "2" when U7(1) is
a
low.
a "0" thereby leaving the number unchanged.
4-212. A19 INTERFACE B ASSEMBLY 05340-60032
4-213. Refer to Figure 8-26 for the schematic diagram.
necessary for completing and displaying a measurement and establishes interconnection with the
A34 ASCII Bus Communicator. The logic level on XA19PlA(D) controls the U1 circuitry to
select either the internal or a n external 10 MHz oscillator with Schmitt triggering circuitry UlA,
buffering.
4-214. The sample rate circuitry, which consists of A19Q1, A19U2A, and A19U14C, determines
the time between measurements. At the end of a measurement XAlgPlA(4) goes low, allowing
or when A19C5 is charging when power is first applied to the instrument.
etc., that are normally internally supplied, must be replaced with signals off the bus. U23 is a
four-pole two position switch that selects resolution information from either the front panel
switch or from U24.
U24 stores the information from the bus when U24(9) is clocked.
recognizes ASCII codes zero through six.
4-216. U17 is also a four-pole two position switch that selects range information from either the,
front panel switch or from U18. When UlS(9) is activated, U18 accepts range information by
recognizing ASCII characters
Table 2-3.
4-217. U25 is a ROM that converts the information on five of the seven ASCII lines to the
required binary code to accbmplish the desired function.
an
4-218. U22A decodes
counter is in remote operation. During remote operation, these two circuits are switched on by a
section of U17 and U23, respectively.
R l
and R2. Sample rate potentiometer
at
the seventh data shift.
At all other times, U7(14) is low.
"S",
"T", "U", or
"F", "G",
and stores ASCII data that restricts the sweep circuits of the
The ASCII codes and frequency ranges are listed in
Theory of Operation
it is
being serially shifted into the
This is accomplished by sub-
This subtracts
(Part
of Option 011)
This board provides control signals
Model 5340A
varies
and
U24
4-45