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design simple, reduce noise, and reduce the quantity of traces susceptible to stray pickup. About 56 dB
rejection of fundamental and 23 dB gain is provided by the harmonic filter amplifier. This allows the '202
to lock at 1466 – 1486 MHz.
A single VCO model is used for both boards. It is an internal Motorola part which is not sold for other
applications. The '192 operates at half the output frequency and step size of the '202. This allows the
same loop filter components to be used. RF is fed to the PLL chip F in input through voltage dividers R14
and R10. These two resistors terminate the PLL chip RF input with 50 ohms and provide isolation.
Both boards use a phase detector current of 2 mA. J1 and J2 are removable jumpers and cut traces.
They are used as connection points for a current measurement of V PD or V CC . A potentiometer VR1 is
used to set M2 (14.4 MHz TCXO) on frequency.
COMPONENTS UNIQUE TO EACH EVK
Components that are not the same on all EVKs are given in the following table:
EXTERNAL REFERENCE INPUT
As shipped, all boards are configured for a 14.4 MHz TCXO (supplied). To use an external reference,
disconnect J13 and connect J9. Use a reference signal at J10 which complies with data sheet require-
ments. Then modify the reference frequency in the program main menu to reflect the changes made ( [F]
menu item ).
DATA TRANSFER FROM COMPUTER TO EVK
To control the serial input EVK with the parallel printer port, a conversion is done. Printer cards are de-
signed to output eight bits through eight lines. A bit mask is used to obtain the bit combination for the
three required output lines (Data, Clock, Load). As bytes are sent to the printer card in sequence, it ap-
pears to be a serial transfer. The printer port is used because data transfer using the serial port is much
slower. A standard IBM PC can support a parallel port data rate of 4.77 MHz.
IBM PCs and compatibles can accept up to three printer port cards. These ports are called LPT1, LPT2,
and LPT3. Each printer card has jumpers or DIP switches on it to set a unique address. Two sets of
addresses are in common use. One set applies to IBM PC XT, AT, and clones. The other is for the PS 2
line. To load data into the EVK, the correct address must be selected. The program default is $278, which
is LPT1 in a clone. If $278 is not the address in use, it must be modified by entering the O menu item in
the main menu. All allowed addresses given in hexadecimal are as follows:
MOTOROLA
'192EVK
U1
MC145192
R2
R8
C22
Not Used
J3
Label
IBM PC and Clones
LPT1
LPT2
LPT3
'202EVK
MC145202
18 kΩ
3.9 kΩ
0 Ω
Not Used
1.0 pF
3 V
5 V
278
378
3BC
PS 2
3BC
378
278
MC145192EVK MC145202EVK
5
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