User manual
52
Serial BUS Analysis
nicantbit)ortheLSB(leastsignicantbit).Thesoftmenu
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.
12.5.2 SPI / SSPI BUS Triggering
After the SPI/SSPI BUSconguration,itwillbepossible
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
beavailableifitwasconguredearlier.PresstheFILTER
button in the TRIGGER section of the control panel to list
all available SPI trigger conditions. The following trigger
conditionscanbedened:
❙ 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
deneaspecicbitsequencewithintheframewhich
start the trigger event. The soft menu key BIT OFFSET
allowsyoutoselecttherstbitofthepredenedbit
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
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
Fig. 12.11: SPI trigger menu
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
denesanystate.Ifyouchoosethehexadecimalinput,
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 several times to close all
menues, and the oscilloscope will trigger on the set bit
sequence. For measurements without measuring object
please refer to chapter 12.2.2.
12.6 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.
12.6.1 UART/RS-232 BUS Conguration
TodecodetheUARTBUSitisnecessarytorstdetermine
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
Fig. 12.12: SPI data trigger menu
Prior to the BUS conguration it is necessary to set the correct
logic level (threshold). Please refer to chapter 4.5. The default
setting is 500 mV.
Fig. 12.13: UART bit sequence
Prior to the BUS conguration it is necessary to set the correct
logic level (threshold). Please refer to chapter 4.5. The default
setting is 500 mV.