N5457A Datasheet, PDF (2/10 Pages) Keysight Technologies – Triggering and Hardware-Based Decode

Introduction
Debugging systems that use an RS‑232 serial bus can be dificult, unless your scope is capable of
triggering on and decoding the RS‑232 protocol. Traditional methods of debugging serial buses such
as RS‑232 include manual bit counting. But this visual technique of counting “1s” and “0s” can be
tedious and it is prone to errors.
Keysight Technologies, Inc. serial bus options for IniniiVision oscilloscopes offer powerful
triggering and provide unique hardware‑accelerated decoding to help you debug embedded designs
with RS‑232 and UART serial buses faster. With the industry’s fastest serial decode update rates, you
can more easily ind and debug random and intermittent errors and signal integrity problems that you
could easily miss using other serial bus decode tools.
Other oscilloscope solutions with serial bus triggering and protocol decode typically use software
post‑processing techniques to decode serial packets/frames. Using these software techniques,
waveform‑ and decode‑update rates tend to be slow (sometimes seconds per update), especially
when you use deep memory, which is often required to capture multiple packetized serial signals.
Figure 1. Deining the RS232/UART protocol structure
Bus coniguration
The RS‑232/UART option for Keysight IniniiVision Series scopes supports a broad range of protocol
structures including many RS‑422 and RS‑485 applications, as shown in Figure 1. Setting up an
IniniiVision Series scope to trigger on and decode your particular RS‑232 or UART bus is easy. You
can select the following settings:
– Number of bits = 5 to 8
– Parity selection = None, odd, or even
– Baud rate = 1200 b/s up to 2.7648 Mb/s
– Polarity = Idle low or Idle high
– Bit order = LSB out irst, or MSB out irst