M e r i d i a n I I U s e r M a n u a l
198
A P P E N D I X K
199
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
Serial Port I/O:
Signal:
I/O port at RS-232 levels for secure, local terminal access.
Parameters:
19200 baud, 8 data bits, no parity, 1 stop bit.
Connector:
Rear-panel DB-9M connector labeled “RS-232”.
To connect to a computer, a null-modem adapter must be used. The serial cable provided with the
shipment is wired as a null-modem. Pinout for the RS-232 console port is shown below.
Note:
For operational details see
Chapter 3 - Console Port Control and Status
.
Meridian II DB9M Pin
Signal Name
1
Not Connected
2
Receive Data (RX)
3
Transmit Data (TX)
4
Not Connected
5
Ground
6
Not Connected
7
Not Connected
8
Not Connected
9
Not Connected
1 PPS Output:
Signal:
Positive TTL pulse into 50
Ω
.
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.
Width:
User selectable to 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.
For RTIC Option see
Chapter 11 - Real-Time Ionospheric Corrections, Specifications
.
Rise Time:
< 2 nanoseconds.
Αlignment:
Within 5 ns of the other TTL outputs in this unit (except the optional DDS).
Connector:
Rear-panel BNC jack on CPU Module labeled “1PPS”.
Note:
To change the pulse width refer to
Chapter 10 - Rear-Panel I/O, 1PPS Output
.
*See
for details.
AM Code Output:
Signal:
Amplitude-modulated (AM), 3:1 ratio, 1 kHz carrier.
Drive:
1 V
RMS
into 50Ω.
Format:
User selectable to IRIG-B (120/IEEE-1344, 122, 123), NASA-36, 2137.
Alignment:
Within 5 us of 1 PPS.
Connector:
Rear-panel BNC jack on CPU Module labeled “AMCODE”.
Note:
To change the time code format refer to
Chapter 10 - Rear-Panel I/O, Time Code Output
.
Summary of Contents for Meridian II
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