VTI Instruments Metek EX1202 User Manual page 65

termination assemblies, which is sufficient to connect any number of instruments, since a
termination is only needed at each end. An example of a three-unit trigger bus installation is
shown in Figure 3-1.
As a general purpose output device, each Trigger Bus channel can be independently programmed
with regards to its output functionality and its static level to assume when enabled as an output.
When not enabled as an output, a channel becomes tri-stated, preventing conflict with other
potential voltage drivers. Regardless of output functionality, each channel provides constant input
functionality. That is, the input level on each channel can be accessed without a specific enable
function call. Moreover, the base functionality of the Trigger Bus channels is not affected by
triggering, scanning, or any other instrument process.
When enabled as an output, each channel also has the ability to generate a 1 µs pulse upon
command. The specific operation of the pulse depends on the static level programmed for that
channel. When a channel is programmed with a static level of high, the pulse will be low-going.
When a channel is programmed with a static level of low, the pulse will be high-going. Each pulse
generation requires a separate function call.
A common application of the pulse generation is multiple-unit synchronization. Referring to
Figure 3-1 above, each unit can be configured to trigger on the same Trigger Bus channel. Then
one unit is selected as a master and is used to output a signal on the designated Trigger Bus
channel line, serving as a common trigger source for all three instruments.
The default selections for each Trigger Bus channel are:

output enable is off

output level is 0
The electrical specifications for the trigger bus are provided in Table 3-.
EX1200 Series Basic Mainframe Operation
F 3-1: T
IGURE RIGGER
Characteristic
Logic Type
V
IT+
V
IT-
V
OS
T 3-4: T B
ABLE RIGGER US
www.vtiinstruments.com
B C E
US ABLING XAMPLE
Value
M-LVDS Type 2
150 mV max
50 mV min
1 V typical
E S
LECTRICAL PECIFICATIONS
65