Keysight 4000 X-Series, Руководство по продвинутой подготовке

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82 4000 X-Series Oscilloscopes Advanced Training Guide
4
Serial Bus Decoding & Triggering, Search & Navigation, and Segmented Acquisition Labs
Your scope should now be decoding I
2
C serial bus traffic as shown in Figure 51 .
We can see automatic decoding of this I
2
C bus in two formats. The blue trace at
the bottom of the display shows time-aligned decoding of the serial bus traffic,
while the lister table at the top of the display shows I
2
C decoding in a tabular
format.
I
2
C addresses can be decoded in either an 8-bit or 7-bit format. The MSB of an
8-bit address byte is the READ/WRITE bit, while the lower seven bits define the
address. The scope already detects the MSB of the address byte and symbolically
decodes it as to whether the address byte is a Read or Write instruction. So the
typical address decoding format most engineers prefer is the 7-bit format, which is
what we have selected. But you also have the option of seeing the address byte in
an 8-bit format, which will include the MSB Read/Write bit.
Note that your scope should still be triggering on random edge crossings of
channel-1. Let’s now set up the scope to trigger when it detects a Read operation
from address = 29
HEX
, following by an “acknowledge”, followed by any data
content (don’t care).
18
Press the
[Trigger]
front panel key; then select Serial 1 (I 2 C) using the Entry knob.
19
Tap the Trigger: Start softkey; then select Frame(Start:Addr 7:Read:Ack:Data) .
20
Tap the Address softkey; then set to 0x29 using the Entry knob.
Figure 51 Decoding I
2
C serial bus traffic.