User manual

User Manual: Agilent Acqiris 10-bit Digitizers Page 20 of 27
The measured performance is then compared to published data sheet specifications. Agilent Technologies tests the
performance corresponding to all data sheet specifications, for all installed options, every time. If we observe your
instrument to be out-of-specification, we always adjust it and re-test before we return it to you.
For more information, or to return your instrument to Agilent for calibration please see
www.agilent.com/find/calibration
3.8. AS bus 2
The digitizers may be used in applications that require many data acquisition channels. In such cases it is possible to
use more than one digitizer in a standard CompactPCI/PXI crate. Each DC Series 10-bit digitizer includes AS bus 2,
a proprietary high bandwidth auto-synchronous bus system that allows multiple digitizers to work together
synchronously.
AS bus 2 distributes both the clock and trigger signals along a plug-in front panel bus, between all the digitizers that
participate in the system. It allows any digitizer to act as the trigger source and any other digitizer to act as the clock
source (acquisition master), enabling all the digitizers to be clocked at the same time. Synchronizing the clock signals
between the devices improves the accuracy of cross-channel measurements and is essential for accurate time
correlation between signals on different channels.
AS bus 2 is intended to connect modules of the same type, i.e. of the same model number, although some exceptions
to this rule might be possible. If modules with the same model number, but different memory length options, are
connected only the shortest memory length can be used.
The AS bus 2 connector is located on the front panel of each module. Bridges are used to connect adjacent modules
for synchronization. An AS bus 2
multi-instrument is activated through software by a function call. Up to 5 6U
modules, or 3 3U modules, may be synchronized with the AS bus 2. Consequently no more than 4 adjacent AS bus 2
bridges should be installed. More detailed information and the commands required to set up the AS bus 2 clock and
trigger distribution are included in the Programmer's Guide and Reference manuals.
3.8. Special Front Panel Inputs and Controls
The following front panel connectors are available:
Connector
Function
MMCX CLK IN
50 Ω External Reference or External Clock Input
MMCX I/O A
User configurable (see below)
MMCX TR OUT
Signal occurs after an accepted TRIGGER.
MMCX I/O B User configurable (see below)
3.8.1. Multi-purpose Input & Outputs (I/O A, I/O B)
The I/O A or I/O B may be used as any of the functions shown in the table below:
Function
Direction
Description
Enable Trigger
Input
10 MHz Ref Clock
Output
To ensure good rise time characteristics the output impedance is 50 Ω This
signal can be used as an input to 1 (or 2 using a T split) CLK IN connectors.
Note: This signal is the internal 10 MHz and is not available if the External
Reference Clock is in use.
Acquisition skipping
to next segment
Output
Acquisition is active
Output Indicates that the acquisition is currently running.
Trigger is armed
Output Indicates that the trigger is armed and waiting for a valid trigger event.
To ensure proper operation of the segment recording of hardware markers, the logical state of MCX I/O A, MCX I/O
B inputs, the input must be stable for a time interval starting 30 ns before the trigger and continuing until 30 ns after
it. This implies that the HF Reject trigger coupling should not be used. If the individual inputs are not in the disable
state the corresponding bits will be useless.
The I/O A and I/O B signals are 3.3 V CMOS compatible, with the following levels: