UART/RS232/422/485 Triggering and Protocol Decode 29
Keysight InfiniiVision HD3-Series Oscilloscopes User's Guide 357
• Bit Order — Selects whether the most significant bit, MSB, or the least significant
bit, LSB, is presented after the start bit in the signal from your device under test.
For RS232 select LSB.
Settings The UART/RS232/422/485 protocol decode mode Settings subtab has these
controls for decode settings:
• Base — Select the base, Hex, Binary, or ASCII, in which decoded words are
displayed.
• When displaying words in ASCII, the 7-bit ASCII format is used. Valid ASCII
characters are between 0x00 and 0x7F. To display in ASCII you must select
at least 7 bits in the Bus Configuration. If ASCII is selected and the data
exceeds 0x7F, the data is displayed in hex.
• When # of Bits is set to 9 in the Bus Configuration, the 9th (alert) bit is
displayed directly to the left of the ASCII value (which is derived from the
lower 8 bits).
• Framing — Enter a value that will be displayed in light blue in the decode
display. A parity error overrides this setting and diplays in red.
Notes • UART/RS232/422/485 protocol decode and triggering is included as a
standard feature.
• If the decode line does not appear on the display, press the [Protocol Decode] key
to turn it on.
• If the oscilloscope is stopped, press the [Run/Stop] key to acquire and decode
data.
• If the setup does not produce a stable trigger, the UART/RS232 signals may be
slow enough that the oscilloscope is Auto triggering. Press the [Mode] key to set
the trigger mode from Auto to Trig'd.
• You can use the horizontal [Zoom] window for easier navigation of the decoded
data.
In the serial decode display, the most significant bit is always displayed on the left regardless
of how Bit Order is set.
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