PCIe-24DSI32
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General Standards Corporation Ph:(256)880-8787 FAX:(256)880-8788 Email: [email protected]
2-4
2.3.2 Single-Ended Input Sources
Single-ended signal sources can be accommodated as shown in Figure 2.3.1b, with the
signal line connected to INP CHAN XX HI, and the associated INP CHAN XX LO input
connected to INPUT RETURN at the source. The single-ended operating connection
provides suitable performance only when the input signal sources either are isolated from
each other, or are common only to a single isolated signal return.
CAUTION: If a significant potential difference exists between the remote signal return and
INPUT RETURN, a low impedance between the two returns can cause
excessive current to flow, which in turn can cause erroneous measurements or
possible damage to the board. Return-current should be controlled to less than
a few milliamps for best performance, and to less than 100 milliamps to avoid
damage.
2.4 Multiboard Clocking and Synchronization
Analog input converters on multiple boards can be:
a. Clocked from a single clock source (Multiboard clocking), and/or:
b. Synchronized to a common time reference (Multiboard synchronization).
Clocking
multiple converters from a single source prevents the
sampling drift
that occurs
when converters are clocked from different sources.
Synchronizing
the converters on
multiple boards causes the converters to initiate conversions simultaneously, and can be
used to eliminate
sampling skew
between channels.
2.4.1 Interboard Connections
Figure 2.4.1 illustrates how multiple PCIe-24DSI32 boards can be daisy-chained together
in an initiator-target sequence to provide common clocking between boards.
The
CLOCK OUTPUT HI/LO lines from an initiator are connected to the CLOCK INPUT HI/LO
lines on a target board, and the SYNC output and input pairs are connected similarly. Each
target board can serve as an initiator for another target board, and multiple boards can be
daisy-chained together for synchronous operation.
Clock
Output
Sync
Output
Initiator Board
Target Board
#1
Clock
Input
Clock
Output
Sync
Output
Target Board
#2
Clock
Input
Clock
Output
Sync
Input
Sync
Output
HI/LO Wire Pairs
Additional
Target Boards
Sync
Input
Figure 2.4.1. Multiboard Clock/Sync Connections
