User manual

54
Serial BUS Analysis
respective symbol. If the input is hexadecimal, only the
entire symbol can be set to X. Use the soft menu key
SELECT SYMBOL to toggle between symbols.
❙ PAT TERN: Offers additional options for UART trigger
settings. The soft menu key SYMBOL OFFSET and the
universal knob are used to select the number of irrelevant
symbols that proceed the pattern within the frame that
are relevant for the trigger event. Any value between 0 to
4095 symbols after the start bit may be entered. Use the
soft menu key NUMB. OF SYMB. to select the number of
relevant symbols as 1, 2 or 3. The number of symbol
denesthepatternsize.Thesymbollength(5to9bit)was
conguredatthetimeofthebusdenitionandwillbe
observed accordingly in the trigger menu. The value input
for the symbols may be binary or hexadecimal (as
described above). Use the soft menu key PATTERN INPUT
for this selection. If binary input is selected, the individual
bits can be assigned via soft menu key SELECT BIT and
the universal knob. The soft menu key STATE allows you
to determine the state for each bit (1, 0 or X). If you
choose the hexadecimal input, the soft menu key VALUE
and the universal knob allow you to set the value for the
respective symbol. Use the soft menu key SELECT
SYMBOL to toggle between symbols. The active byte will
be marked with a green border in the display window of
the trigger condition.
❙ PARITY ERROR:Triggerwithaparitylter
❙ FRAME ERROR: Trigger with a frame error
❙ BREAK: Trigger with a break. The BREAK condition is
fullledifastopbitdoesnotsucceedastartbitwithina
speciedtimeperiod. The stop bits low are active during
the break.
Press the MENU OFF button several times to close all
menus, and the oscilloscope will trigger on the set bit
sequence. For measurements without measuring object
please refer to chapter 12.2.2.
12.7 CAN BUS
The CAN bus (Controller Area Network) is a bus system
primarily developed for automotive applications and is
used for the data exchange between controller units
and sensors. It can be found increasingly in the aviation,
healthcare, and general automation industries. At the
Fig. 12.16: UART trigger menu page 2
physical level, CAN is a differential signal, therefore a diffe-
rential probe (e.g. HZO40) is recommended for decoding,
although standard probes are equally suitable to capture
the signals. The standard data rates range between 10
kBit/s and 1 MBit/s. A CAN message primarily consists of
a start bit, the Frame ID (11 or 29 bit), the data length code
DLC, the data, a CRC, acknowledge and an end bit.
12.7.1 CAN BUS Conguration
After choosing the BUS type CAN in the BUS menu the
congurationmenuwillopenafterpressingthesoftmenu
key CONFIGURATION. In the menu that opens you can
press the top soft menu key DATA to select the desired
channel via universal knob in the CURSOR/MENU section.
An analog or a digital channel can be connected to CAN-
High or CAN-Low. In addition, it is possible to connect a
differential probe (e.g. HZO40) to an analog channel. When
using a differential probe, select CAN High if the positive
input of the probe is connected to CAN-H and the negative
input to CAN L. If the probe is connected with reversed
polarity, you must select CAN L.
The soft menu key SAMPLE POINT allows you to specify
the exact point within the bit at which the value for the cur-
rent bit is sampled. You can select a value in percent (25%
to 90%) via universal knob or KEYPAD key in the CURSOR/
MENUsection.TheoptionBITRATEdeneshowmany
bits are transmitted per second and allows you to select
default data rates (10 / 20 / 33.333 / 50 / 83.333 / 100 / 125
/ 250 / 500 kBit/s and 1 MBit/s) via universal knob. Use the
softmenukeyUSERtospecifyuser-denedbitrates.You
can enter the value via universal knob or numeric input
(KEYPAD button).
Prior to the BUS conguration it is necessary to set the correct
logic level (threshold). Please refer to chapter 4.5. The default
setting is 500 mV.
Fig.12.17:SettingtheSAMPLEPOINTduringtheCANconguration
For CAN BUS trigger and decoding you need the R&S®HOO12
option or the upgrade voucher R&S®HV112.