HP 5340A Operating And Service Manual page 93

Model 5340A
Theory of Operation
4-219. Counter U3 identifies what digit is currently being shifted in the serial display. U21
compares this data with the RESOLUTION information and subtracts a "2" offset at the
appropriate time during a phase lock measurement. For direct count measurements, a zero is
subtracted, leaving the number unchanged. U4C detects the seventh character shift. U15 is used
to strobe output data into U11 by comparing counts from U3 a n d U12.
4-220. At the completion of a measurement for which a n ASCII output is desired, U22A will set,
supplying a low on U16C(10). An output is also generated when the TALK line (Jl-8) is driven
low by the controller, this is gated along with the PE line from A21 to set U8A, causing U8A(5)
to give a high to A21 and A34.
4-221. U12 is a 16 presettable counter that sets to
switches U6 to read the output of U12. Character "10" is detected by U4A.
4-222. The logic level of the Inhibit line a t PlA(N) is low for Phase Lock measurements and
drives U6(2) low. The ROM interprets this data and outputs a n ASCII "L" to indicate the Phase
lock mode. When PlA(N) is high, the ROM outputs a n ASCII "D" to indicate the Direct mode.
4-223. A21 then sets DAV low, indicating to the bus that this data is valid, and then again goes
high, incrementing counter U12 to 14. This code causes U6 to select the output of U12, which
causes U7 to output the ASCII code for "space", or overflow, if overflow has occurred. DAV
again cycles and U12 increments to 15, which similarly causes
to 0 (zero). This causes U6 to select the output of four pole switch U5, which is accepting dis-
played digit information from quad flip-flop U11. Eight digits of data are processed as U12 counts
from 0 to 7. When U12 increments to 8, the output of U12 is fed through U6 to U7, which con-
verts the da.ta to a n ASCII "E" (for exponent). U12 increments to 9 and similarly a
generated. U12 increments to 10, U6 selects the output of U5, and U5 reads the setting of the
resolution switch. This supplies the exponent for the measurement. U12 increments to 11 and
U7 supplies the ASCII code for "Cr" (carriage return); U12 increments to 12 and U7 supplies a
"Lf' (line feed).
4-224. As a n example of operation, assume that a 1.2345 GHz signal is measured with 100 kHz
resolution. A typical output sequence is as shown below:
4-225. The data is read 12345 x lot5 Hz, which is 1.2345 GHz. The L indicates that this
measurement was made usidgi the phase lock technique.
4-226. U7(9) goes low at Lf (line feed), and this is clocked into U8A. This indicates to Control
Board A21 that the output sequence is complete.
4-46
when the PE line (PlA-15) goes low.
13
U12 Count U7 Output
13 L
14
15
0 0
1
2 0
3 1
4
2
5 3
6
4
7 5
8 E
+
9
10 5
11
12
a
"space". U12 then increments
is
"+"