EndRun Meridian II, User Manual, Page: 124 / 240

M e r i d i a n I I U s e r M a n u a l 104
C H A P T E R T E N
105 M e r i d i a n I I U s e r M a n u a l
R E A R - P A N E L I / O
help triggerppo
Direct Digital Synthesizer (DDS) Option
The DDS Option provides user-selectable pulse rates from 1 Hz to 10 MHz, programmable in 1 PPS
steps, including 1.544 MPPS or 2.048 MPPS. The selected pulse rate is phase locked to the system
oscillator and is not aligned with system time.
The DDS is a “system signal”. This means that there is one DDS signal that affects the whole sys-
tem. In other words, if your Meridian II has multiple DDS outputs and you change the pulse rate,
then all DDS outputs will be affected.
The pulse rate is 0 Hz when shipped from the factory but can be changed (see below). For details
on the DDS signal definition see
Appendix K - Specifications, Optional Direct Digital Synthesizer
(DDS) Output on CPU Module .
View the DDS Connector
On the front-panel display traverse to the Main Menu and then to CPU_I/O. This display lists any
connector on the CPU Module that has an optional I/O signal. Connectors are identified as A, B or C.
Select the particular connector (I/O-A, I/O-B or I/O-C) to see which signal is installed.
Or, you can use this console port command:
Command:
cpuio
MeridianII reply:
CPU I/O C - DIRECT DIGITAL SYNTHESIZER OUTPUT is Installed
Current Setting = (See systemio command)
Change the DDS Rate
On the front-panel display traverse to the Main Menu and then to Sys_I/O. If a DDS output is
installed in your unit, then there will be a selection for DDS-Out. Select this and you will be able to
change the rate. Available pulse rates are 1 Hz to 10 MHz, in 1 PPS steps.
Or, you can use these console port commands:
Command:
systemio
MeridianII reply:
System I/O Signal DIRECT DIGITAL SYNTHESIZER OUTPUT Installed
Current Setting = 0 Hz
Command:
systemioconfig
MeridianII reply: Interactive script is started so you can change the pulse rate.
10 MPPS Output Option
The 10 MPPS Rate Output Option provides an on-time pulse rate. For details on signal definition see
Appendix K - Specifications, Optional 10 MPPS Output on CPU Module
.