User manual

54
Serial Bus Analysis
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 me-
nus, and the oscilloscope will trigger on the set bit se-
quence. For measurements without measuring object ple-
ase refer to chapter 12.2.2.
12.7 CAN BUS
The CAN bus (Controller Area Network) is a bus sys-
tem 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 phy-
sical level, CAN is a differential signal, therefore a differen-
tial probe (e.g. HZO40) is recommended for decoding, alt-
hough 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.
Fig. 12.17: UART trigger menu page 2
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 spe-
cify the exact point within the bit at which the value for
the current bit is sampled. You can select a value in per-
cent (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 nu-
meric input (KEYPAD button).
12.7.2 CAN BUS Triggering
After the CAN BUSconguration,itwillbepossibletotrig-
ger on various events. Press the TYPE button in the TRIG-
GER section and choose the soft menu key SERIAL BU-
SES. Then press the SOURCE button in the TRIGGER sec-
tion and choose CAN. This will only be available if it was
conguredearlier.PresstheFILTERbuttonintheTRIGGER
section to list all available CAN trigger conditions:
❙ START OF FRAME: Triggersontherstslopeofthe
SOF bit (synchronizing bit).
❙ END OF FRAME: Triggers on the end of the frame.
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.12.18:SettingtheSAMPLEPOINTduringtheCANconguration
For CAN BUS trigger and decoding you need the R&S®HOO12 op-
tion or the upgrade voucher R&S®HV112.