Microchip Technology SA5 Series, Руководство пользователя

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Product Overview
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2019 Microchip Technology Inc. DS50002938A-page 13
tings can be adjusted independently, however, the MAC can only discipline to one input
at a time. If a valid PPS signal on the selected input is present, then the parameter
PpsInDetected
= 1. See Section 3.4 “1PPS Disciplining” for more details.
CAUTION
An LVDS square wave 1PPS is the allowable input.
10 MHz Output
The 10 MHz RF output appears on Pin 3 as soon as the MAC is switched ON and is
always present, regardless of the lock status. When the MAC is out of lock
(
Locked
= 0/Logic-High BITE pin), the output frequency is provided by the free-running
TCXO, which has frequency accuracy specification of ±2 ppm over its operating range.
The output format is 3.3V LVCMOS compatible.
Note: If a high-level (high-power) output driver is required, a driver circuit must be
implemented external to the MAC.
1PPS Output
An LVDS 1 pulse-per-second (1PPS) square wave output is available on pins J1-17,19
upon power-up. The 1PPS output is derived by digital division of the RF reference fre-
quency and cannot be de-coupled. Therefore, the 1PPS and 10
MHz outputs are
always synchronized (within ±50 nanoseconds, regardless of Lock status).
PPS output timing relative to average PPS input timing is adjustable via the digital inter-
face with 10
ns steps using
PpsOffset
parameter.
Default PPS Pulse Width is 20 μ s. Pulse width may be modified via the
PpsWidth
parameter.
BITE Output
The SA5X provides an active logic low indication through Pin 6, the BITE signal, when
the internal quartz oscillator is frequency-locked to the rubidium atomic resonance. As
long as the BITE signal is low, the user can be assured that the short-term stability
specifications are satisfied. The lock status is also available through the C3 Protocol
Locked
parameter.
If the BITE signal is high (
Locked
= 0), then atomic Lock is not attained (or is lost) and
the SA5X is in its start-up sequence. During this sequence, signal output amplitude is
maintained but the stability performance is driven by the internal TCXO. Lock acquisi-
tion typically takes 5 minutes at room temperature.
Alarm Output
The Alarm Output provides an indication if an alarm is present (active logic low). It will
persist until cleared with the
ackalm
software command. A user can learn the exact
alarm condition from the value of the
Alarms
parameter (See Section 4.4.3 “Alarms
Parameter” ).
1.4 CONFIGURATION MANAGEMENT
The Command Line Interface can be used to control specific functions of the MAC from
a terminal connected to the RS-232 serial port or the USB port.
Refer to
Chapter 4. “Command Line Interface” for further details.