User manual

45
Serial Bus Analysis
❙ Noacknowledgetoconrmdatareception
❙ Duplex capability
Most SPI buses have 4 common lines, 2 data lines and 2
control lines:
❙ Clock to all slaves (SCLK)
❙ Slave select or chip select lines (SS or CS)
❙ Master-Out-Slave-In, Slave-Data-Input (MOSI or SDI)
❙ Master-In-Slave-Out, Slave-Data-Output (MISO or SDO)
If the master generates a clock pulse and selects a slave,
data can be transmitted in either one direction or
simultaneously in both directions (only available with
HOO10/HV110).
13.5.1 SPI / SSPI BUS Conguration
Certain settings are necessary to guarantee that a SPI bus
is decoded correctly. First, you have to determine if a SPI
system with or without chip select is available (2-wire or
3-wire SPI). This can be done in the BUS setup menu when
selecting the BUS type. For a 2-wire SPI system, select the
option SSPI; for a 3-wire SPI system, select the option SPI.
Then press the CONFIGURATION button to open the setup
menu for SPI. Use the top soft menu key SOURCE to se-
lect the respective channel for chip select (CS), clock (Clk)
and data. Select the respective soft menu key CS, Clk or
Data and then use the soft menu key DATA and the univer-
sal knob to the select the respective source channel. For
the 2-wire SPI, select the possible TIME OUT instead of a
chip select source. During the time out, data and clock line
are at Low. When the time out has been reached, a new
frame begins. If the time intervals between the data pa-
ckets are shorter than the time out, these packets belong
to the same frame. You can select the dead time via uni-
versal knob or via numeric input (KEYPAD button). A small
window provides information about the current settings.
In addition to assigning the source, the soft menu key AC-
TIVE allows you to select the following settings:
❙ CS: Chip select high or low active (low active is the
default setting)
Fig.13.6:SimplecongurationofSPIBUS
Fig.12.12:SimplecongurationofaSPIBUS
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. For 3-wire SPI the external trigger input will
be used a CS (Chip Select). The threshold can be set in the BUS
conguration menu.
If the option HOO11 resp. the voucher HV111 is installed, it it only
possible to select analog channels as source. If the option HOO10
resp. the voucher HV110 is installed, both analog and digital
channels are available as source.
❙ CLK: Data will be stored with rising or falling slope (rising
slope is the default setting)
❙ DATA: Data high or low active (high active is the default
setting)
You can use the soft menu key BIT ORDER to determine if
the data of each message starts with the MSB (most sig-
nicantbit)ortheLSB(leastsignicantbit).Thesoftmenu
key WORD SIZE allows you to select via universal knob
how many bits are included per message. You may select
any value between 1 and 32 bits.
13.5.2 SPI / SSPI BUS Triggering
After the SPI/SSPI BUSconguration,itwillbepossible
to trigger on various events. Press the TYPE button in the
TRIGGER section of the control panel and choose the soft
menu key SERIAL BUSES. Then press the SOURCE button
in the TRIGGER section and choose SPI Bus. This will only
beavailableifitwasconguredearlier.PresstheFILTER
button in the TRIGGER section of the control panel to list
all available SPI trigger conditions.
The following triggerconditionscanbedened:
❙ FRAME START: Sets the trigger event on the start of the
frame. The frame starts when the chip select (CS) signal
switches to the selected active mode.
❙ FRAME END: Sets the trigger event on the end of the
frame. The frame ends when the chip select (CS) signal
switches from the selected active to the inactive mode.
❙ BIT: Selects the trigger time to the set bit within the set
bit sequence with the universal knob in the CURSOR/
MENU section. You can also enter a numeric value to
determine the desired bit number (KEYPAD button).
❙ SER. PATTERN: Use the soft menu SER. PATTERN to
deneaspecicbitsequencewithintheframewhich
start the trigger event. The soft menu key BIT OFFSET
allowsyoutoselecttherstbitofthepredenedbit
sequence within the frame. The bits in front of it have no
impact on the trigger event (for instance, if the bit offset =
2, bit 0 and bit 1 after CS will be ignored and the pattern
begins with bit 2). You can select a value between 0 and
4095 via universal knob or enter it numerically (KEYPAD
Fig.13.7:MenuforthedenitionofaSPI bus
button). The soft menu key NUMBER OF BITS allows you
to select how many bits will be analyzed for the trigger
condition. You can select a value between 1 and 32 bit via
universal knob. The serial bit sequence (PATTERN INPUT)
can be entered as binary or hexadecimal value. If you
choose the binary input, the soft menu key SELECT BIT
and the universal knob allow you to select which
individual bits within the data are to be edited. The option
STATE allows you to assign a logic state to each bit (High
= H = 1, Low = L = 0 or X = don’t care). The state X
denesanystate.Ifyouchoosethehexadecimalinput,
the soft menu key VALUE and the universal knob allow
you to set the value for the respective nibble (4 bit). If the
input is hexadecimal, only the entire nibble can be set to
X. Use the soft menu key SELECT NIBBLE to toggle
between nibbles. The active nibble will be marked with a
green border in the display window of the trigger
condition.
Press the MENU OFF button three times to close all
menus, and the oscilloscope will trigger on the set bit
sequence.
Formeasurementswithoutmeasuringobjectpleaserefer
to chapter 10.2.5.
13.6 UART/RS-232 BUS
The UART bus (Universal Asynchronous Receiver Trans-
mitter) is a general bus system and the base for many pro-
tocols. One example is the RS-232 protocol. It consists of a
frame with a start bit, 5 to 9 data bits, one parity bit and a
stop bit. The stop bit can assume the single length, or 1.5
or twice the length of a normal bit.
13.6.1 UART/RS-232 BUS Konguration
TodecodetheUARTBUSitisnecessarytorstdetermine
which channel will be connected to the data line. This
setting is selected after choosing the bus type UART in the
BUS menu and pressing the soft menu key CONFIGURA-
TION. In the menu that opens you can press the top soft
menu key DATA SOURCE to select the desired channel via
universal knob.
The soft menu key ACTIVE can be used to determine if
the data transferred to the BUS are active high (High = 1)
or active low (Low = 1) (for RS-232, choose Low). Use the
soft menu key SYMBOL SIZE and the universal knob to
select a value between 5 bit to 9 bit for the bits that form a
symbol. Another setting can be selected via soft menu key
PARIT Y.
For UART/RS-232 BUS trigger and decoding you need the HOO10
resp. HOO11 option or the upgrade voucher HV110 resp. HV111.
Fig. 13.8: UART bit sequence
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.