Tektronix 494AP service manual Vco, Lsb, DB6 DB2 DBO, DB2-DBO

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	Table6-13(cont)
Data Bits
7 6 5 4 3 2 1 A	Descrlption

J.Preselector Driver(77)

0 l x x x x x x	-conversion,g2gMHzofiset
l 0 x x x x x x	+conversion,
	829MHzoffset

Mafntenanca- 494A1494ApServiceVol. 1

	Table6-13(contl
DataBits
7 6 5 4 3 2 1 0	DescripUon

LAuxlllary Syntheslzer Control (7D)(cont)

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0 0 x x x x x x					829 MHztF not usEd
x x l x x x x x					Driver output filter on (for narrow
x	x 0		x x x		spans)
		X		X	Driveroutputfilter off
x	x x	1 x x x		x	Preselector
x	x x	0	x x x	x	LPFswitch	switch
x	X X	x	l x x	x	lst LO FM coil not swept
x	x x	x	0 x x	x 1st LO FM coitswept
x	x x	x	x l x	x	Driveron
x	x x	x	x 0 x	x	Driverofi (for degauss)
x	x x	x	x x x	1	3rd harmonic1st LO conversion
x	x x		x x x		l s t	LO conversion

K.CENTER/MKR FREQUENCYCon- trol

0 1 0 1 x 1 0 1

0 0 0 0 x 1 1 0

0 0 0 0 x 1 1 1

A A A A x 0 0 0

0 0 0 A x 0 0 1

N N N N x 0 t 0 0 0 N N x 0 1 1 0 0 0 0 x 1 0 0

M. Phase Lock Control

This sectionsets R, the reference divider to 5 yietdinga 20O kHz referencefrequency.

This sectionsets the value of A from 0 to 31

LSB

Thissectionsets N from 3.1to 34

31-1111 32-0000
01	.r0
33*0001	34-0010
1 0	1 0

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Control(70)

Write (73)

J

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l x x x x x x x 0 x x x x x x x x 0 x x x x x x

x x 0 x x x x x

x x x 0 x x x x

x x x x l x x x x x x x 0 x x x x x x x x 0 x x

x x x x x x 0 x

x x x x x x x 0

DB7-DBO

D87

1st LO storagegateopen 1st LO storagegateclosed Steers DAC data to 1st LO high byte

Steers DAC data to ist LO mid byte

Steers DAC data to 1st LO low byte

2nd LO storag€gateopen 2nd LO storagegateclosed steers DAC data to 2nd Lo high byte

Steers DAC data to 2nd LO mid byte

Steers DAC data to 2nd LO low byte

DACData(71)

Data for centerfrequencyDAC(s) steeredby controlregister

CENTER/MKRFREQUENCyCon- trol Read (F0)

1st LO DAC storedvoltagecom_ parator

l x x x x x x x x x l x x x x x x x x l x x x x

x x x x l x x x

x x x x x x l x

DB6

DB2

DBO

l x x x x x x x

x l x x x x x x

x x l x x x x x DB4-DBO

N. Front Panel

Glocksdataon DBointo a tatch Clearsthe counters TransfersDBOserial data to con- trol latch outputs

Resetsthe counteroutputregister selector

TransfersDBo serialdata to syn- thesizerN latches

Gatemodelatch NVRAMswitchlatch

Serial data for control of syn- thesizerN latches

Read(F3)-Most SlgnlficantByte

Enor voltage below a preset amount

Error voltage above a preset amount

Validcountis in counters Upperfive bits of counteroutput; the remaining16 bits are in the followingtwo bytes

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D B O

L.Auxiliary Synthesizer Control(7D)

2nd LO DAC storedvoltagecom- parator

Reading Data From Swilch

Encoders(F4)

l x x x x x x x CENTER/MKR FREQUENCY down

0 x x x x x x x CENTER/MKRFREQUENCYup

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DB7-D84	synthesizer
DB2-DBO	chipdata(D3-D0)
	Synthesizer chip addresses
x x x x l x x x	(A2-A0)
	VCOenable
x x x x 0 x x x	vco

DB6-DBO Switchcodes (see Figure7-33 in

Section7)

6-6r

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