Vertex Standard VX-2000U, Service Manual

Page: 18 / 65

18
Circuit Description
Channel Selection & Display
(4-channel version)
The C
HANNEL
button on the front panel causes
microprocessor Q1039 to select the operating fre-
quency and CTCSS frequency data from serial
EEPROM Q1048 (
BR93LC66AF
). The operating
frequency data is in the form of PLL dividing
ratios, which are passed to the PLL IC on the
M
AIN
Unit via strobe, data, and clock outputs on
pins 43, 42, and 41 respectively. The channel digit
display data from the microprocessor is strobed
by pin 46 to display latch Q2002 (
BU4094BCFV
)
on the D
ISPLAY
-1 Unit, which decodes the data
and drives the four channel LEDs and the func-
tion indicator LEDs.
Channel Selection & Display
(40-channel version)
The U
P
and D
OWN
buttons on the front panel
cause microprocessor Q1039 to select the oper-
ating frequency and CTCSS frequency data from
serial EEPROM Q1048. The operating frequency
data is in the form of PLL dividing ratios, which
are passed to the PLL IC on the M
AIN
Unit via
strobe, data, and clock outputs on pins 43, 42,
and 41 respectively. The channel digit display
data from the microprocessor is strobed by pin
46 to display latch Q3001 (
DN8657S
) on the D
IS
-
PLAY
-2 Unit, which decodes the data and drives
the two 7-segment LEDs and the function indi-
cator LEDs.