User manual

48
Serial Bus Analysis
view (blue highlighted). By default, the table is displayed at
the bottom of the screen. Generally, a complete message
of a protocol is displayed in a row. The columns include
important information, e.g. address and date of the mes-
sage. The number of rows in the table is identical to the
number of complete message frames in storage. The de-
codingresultsmaybesavedasCSVlebyusingthesoft
menu key SAVE (e.g. save to a USB stick).
Example of I
2
C BUS table:
“Bus table: BUS1 (I2C: Clock SCL = D0, Dates SDA = D1)“
Frame,Mark,Start time[s],Type,ID,Length,Date,Condition
1,,-197.89200e-6,Read,0x2D,5,0xF110E55D31,OK
2,,28.00000e-9,Write,0x42,8,0xEB8DC599AE5D6FC0,OK
3,,217.74000e-6,Write,0x3B,6,0xA113B7263E5B,OK
4,,376.07200e-6,Read,0x0E,6,0x55C3EB71D9E8,OK
5,,613.58000e-6,Write,0x66,8,0x91B86EE6655E2300,Data Error
The soft menu key TRACK FRAME allows you to scroll
through the BUS table and simultaneously jump to the cor-
responding position in the memory via universal knob to
display details on the screen. However, this is only pos-
sible if acquisition has been stopped. This option is also
available in the short menu BUS via soft menu key TRK (=
Track). If you activate the soft menu key FRAME TIME DIF-
FERENCE (highlighted in blue), the time difference to the
previous frame (data packet) will be displayed in the BUS
table. This column will be labeled in the table as TIME
DIFF. If this function is deactivated, the absolute time in re-
lation to the trigger point will be displayed in the column
START TIME. The soft menu key TAB in the BUS short
menu allows you to activate or deactivate the BUS table
without opening a menu. You can use the soft menu item
POSITION to move the table to the top or bottom of the
screen. In addition, it is possible to display the BUS table
in full screen. Select the position via universal knob in the
BUS menu or directly via soft menu key POS in the BUS
short menu.
Fig. 12.2: Example I
2
C BUS with BUS table
Make sure that a complete message of a serial protocol is always
displayed on the screen to ensure decoding can function pro-
perly. The Zoom function allows you to view details for any speci-
c message.
A BUS table can only be stored if the STOP mode is active.
12.2.2 Bus Signal Source
The R&S®HMO Compact series features 4 contacts left of
the channel CH1 which provide the following signals ac-
cording to the respective settings:
❙ Square wave: Probe compensation (standard setting),
frequency 1 kHz or 1 MHz.
❙ SPI: Data rates 100 kbits/s, 250 kbits/s or 1 Mbits/s
❙ I
2
C: Data rates 100 kbits/s, 400 kbits/s or 1 Mbits/s
❙ UART: Data rates 9600 bits/s, 115.2 kbits/s or 1 Mbits/s
❙ Pattern: Frequency 1 kHz or 1 MHz
❙ Counter: Frequency 1 kHz or 1 MHz
The contact at the upper left is always ground and the sig-
nal levels are about 1 V. The following table shows how the
four outputs S1, S2, S3 and
are used, depending on the
signal.
Signal S1 S2 S3
Square Wave No Signal No Signal No Signall Square Wave
SPI Chip Select
Low Aktive
Clock,
Rising Edge
Data,
High Active
No Signal
I
2
C No Signal Clock SCL Data SDA No Signal
UART No Signal No Signal Data No Signal
Pattern Bit 0 Bit 1 Bit 2 Bit 3
Counter Bit 0 Bit 1 Bit 2 Bit 3
Press the key SETUP in the GENERAL section and the
PROBE ADJUST & BUS SIG. SOURCE to open the BUS
signal source menu on page 2|2. Now you can select the
operational mode for the bus signal source. An information
box is displayed for each operating mode, displaying the
corresponding connector assignment. By pressing the re-
spective soft menu key, you can open a submenu with the
bit rate setting of the selected operating mode. The square
wave signal for probe compensation is available with 1 kHz
(low frequency compensation) and 1 MHz (high frequency
compensation). In the automatic mode (standard setting),
the output will provide 1 kHz at sweep speeds from 100 µs/
div, at faster sweep speeds 1 MHz will be available. These
signals allow to check the settings for parallel and optional
serial bus analysis.
Fig. 12.3: I
2
C BUS signal source
Tab. 13.1: Pin assignment of the BUS signal source