Circuit Description
78
CG635 Synthesized Clock Generator
+Q_TST:
Offset, scaled and filtered (with 180 Hz bandwidth) version of the front panel
Q output. Useful for testing and calibrating the amplitude and offset of the Q output
provided that the user load is disconnected from the instrument. Transfer function:
+Q_TST = 0.285 × (+Q_OUT + 4.096 V).
–Q_TST:
Offset, scaled and filtered (with 180 Hz bandwidth) version of the front panel
Q
¯ output. Useful for testing and calibrating the amplitude and offset of the Q
¯ output
provided that the user load is disconnected from the instrument. Transfer function:
–Q_TST = 0.285 × (–Q_OUT + 4.096 V).
CMOS_TST:
Offset, scaled and filtered (with 140 Hz bandwidth) version of the front
panel CMOS output. Useful for testing and calibrating the amplitude and offset of the
CMOS output provided that the user load is disconnected from the instrument. Transfer
function: CMOS_TST = 0.444 × CM 0.455 V.
+24V_TST:
Scaled and filtered (with 120 Hz bandwidth) version of the +24 V power
supply. +24V_TST = 0.130 × +24 V (unswitched) power supply. The scaling network
has a high impedance so as to source only 200 µA from the +24 V standby power supply
when the instrument is turned “off”.
RS-232 Interfaces
RTS_RS232:
Request-to-Send input to CPU from the rear panel RS-232 interface.
RXD_RS232:
Serial data input to CPU from the rear panel RS-232 interface.
RXD_RB:
Serial data input to CPU from the optional rubidium timebase.
CTS_RS232:
Clear-to-Send output from CPU to the rear panel RS-232 interface.
TXD_RS232:
Serial data output from CPU to the rear panel RS-232 interface.
TXD_RB:
Serial data output from CPU to the optional rubidium timebase.
Digital Inputs to Microcontroller
-DROPOUT:
Status bit goes low to generate an –XIRQ (non-maskable interrupt
request) when the unit is turned “off” or when the power is removed.
-GPIB:
Status bit goes low to generate an –IRQ (maskable interrupt request) when the
GPIB interface requires service.
10MHZ:
10 MHz square wave processor clock derived from the 20 MHz timebase.
KEY0-KEY4:
Five key strobe lines. One of the five lines will go “high” when a front
panel key is pressed during the column strobe period for that key. All five inputs have
their active pull-downs enabled.
-DONE:
This line goes low when the phase jump requested of U408 has been
completed.