M e r i d i a n I I U s e r M a n u a l
204
A P P E N D I X K
205
M e r i d i a n I I U s e r M a n u a l
S P E C I F I C A T I O N S
CPU Module Options
Optional 1 PPS (RS-422) Output (CPU Module):
Signal:
RS-422 levels.
RS-422 (100
Ω
differential): V
DIFF
(min)=2.1V, V
DIFF
(nom)=2.4V, V
DIFF
(max)=3.0V,
V
OUT
(max)=3.3V referenced to GND.
User-Selectable Width:
20 us, 1 ms, 100 ms, 500 ms.
User Calibration:
+/- 500 us, 1 ns resolution.
Accuracy:
<10 nanoseconds RMS to UTC(USNO) when locked.*
Stability:
TDEV < 10 ns @
τ
< 10
5
seconds,
σ
y
(
τ
) < 6.0x10
-14
@
τ
=10
5
secs.
Rise Time:
< 3 nanoseconds.
Αlignment:
Within 5 ns of the TTL outputs in this unit (except the optional DDS).
Connector:
Rear-panel BNC jack labeled “1PPS RS-422”.
Pinout:
Pin 3 is +signal. Pin 6 is -signal. Pin 5 is GND.
Note:
To change the pulse width refer to
Chapter 10 - Rear-Panel I/O, 1PPS Output
.
*See
for details.
Optional DC Code Output (CPU Module):
Signal:
Positive TTL pulse into 50
Ω
(DC Level Shift) or RS-422.
TTL (50
Ω
to GND): V
OL
(max)=0.4V, V
OH
(min)=2.4V, V
OH
(nom)=2.5V, V
OH
(max)=3.0V.
RS-422 (100Ω differential): V
DIFF
(min) = 2.1V, V
DIFF
(Nom) = 2.4V, V
DIFF
(max) = 3.0V,
V
OUT
(max) = 3.3V referenced to GND.
Format:
User selectable to IRIG-B (000/IEEE-1344, 002, 003), NASA-36, 2137.
Rise Time:
< 2 nanoseconds (TTL). <3 nanoseconds (RS-422).
Alignment:
Within 5 ns of the other TTL outputs in this unit (except the optional DDS).
Connector:
Rear-panel BNC jack labeled “DCCODE”.
Note:
To change the format refer to
Chapter 10 - Rear-Panel I/O, Time Code Output
.
Optional Programmable Pulse Output (PPO) (CPU Module):
Signal:
Positive TTL pulse into 50
Ω
or RS-422.
TTL (50
Ω
to GND): V
OL
(max)=0.4V, V
OH
(min)=2.4V, V
OH
(nom)=2.5V, V
OH
(max)=3.0V.
RS-422 (100
Ω
differential): V
DIFF
(min)=2.1V, V
DIFF
(nom)=2.4V, V
DIFF
(max)=3.0V,
V
OUT
(max)=3.3V referenced to GND.
Rate:
User selectable to 1, 10, 100, 1k, 10k, 100k, 1M, 5M, 10M PPS, 1PPM, 1PP2S, Inv1PPS*.
Accuracy:
< 6x10
-14
to UTC for 100k second averaging times when locked.
Stability:
TDEV < 10 ns @
τ
< 10
5
seconds,
σ
y
(
τ
) < 6.0x10
-14
@
τ
=10
5
secs.
Duty Cycle:
50% except 1PPS which mimics the standard 1PPS Output defined above.
Rise Time:
< 2 nanoseconds (TTL). < 3 nanoseconds (RS-422).
Alignment:
Within 5 ns of the other TTL outputs in this unit (except DDS, if any).
Connector:
Rear-panel BNC jack labeled “PPO”.
Note:
To change the selection or to use the TriggerPPO function, refer to
Chapter 10 - Rear-Panel
I/O, Programmable Pulse Output (PPO) Option
.
*Inverted 1PPS (falling edge on-time) available in 1U and 2U.
Summary of Contents for Meridian II
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