Astronics OMNIBUS II NI PXIe, Руководство пользователя

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MODULE CONFIGURATIONS
6-2 OmniBus II NI PXIe User Manual
Level Designator→
S P
Level Number used in Part No.→
1 5
Number of Simultaneous Terminals 32 32
Concurrent BC and RT Simulation

Configurable RT Response Time
 
Monitor
 
Filtering for terminal address
 
Filtering for subaddress

Concurrent terminal monitoring

Protocol Error Injection

Variable Transmit Amplitude

Zero Crossing Distortion

Table 6.3—MIL-STD-1553 Level Function Definition
The MIL-STD-1553 modules also contain avionics discrete I/O, see Section 4.5
for more details.
6.2.1 Software-Selectable Bus Termination
When direct-coupled, each databus on the OB2 MIL-STD-1553 module has a 75-
Ω termination resistor. This resistor can be switched across the terminals under
software control. When the bus is transformer coupled, the direct-coupled
termination resistance must be off, and external couplers and terminators are
required. See Appendix A: Coupling and Termination for more information about
bus termination and transformer versus direct coupling.
6.2.2 Configurable RT Response Time
The RT response time of MIL-STD-1553 OB2 modules may be individually set in
software for each 1553 channel. You can measure the response from the mid-bit
zero-crossing of the parity bit to the mid-bit zero-crossing of the status word sync.
The RT response time may be set through software using the
BTI1553_RTResponseTimeSet function. The response time value is an
integer that represents the response time in hundreds of ns up to 819 μs. The error
checking process affects the minimum response time and is about
3.7 μs for MIL-
STD-
1553A and 7.7 μs for MIL-STD-1553B (the default protocol in
BTI1553_RTConfig
). Any value below the minimum yields the minimum. The
default RT response time for OB2 modules is approxi
mately 9 μs (a value of 90).
The exact response time depends on several factors, such as where on the bus it is
measured, analog and digital delays in the onboard circuits, and uncertainty due to
the 100-ns sampling time.
6.2.3 Variable Transmit Amplitude
For OB2 MIL-STD-1553 level P channels, the amplitude of the transmitted
databus signal can be varied under software control. Using
BTI1553_Param-
AmplitudeConfig
, the OB2 has extended functionality from the OmniBus