User manual

52
Serial Bus Analysis
ton in the TRIGGER section and choose SPI Bus. This will
onlybeavailableifitwasconguredearlier.PresstheFIL-
TER 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
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.
Fig. 12.11: SPI trigger menu
Press the MENU OFF button several times to close all me-
nues, and the oscilloscope will trigger on the set bit se-
quence. For measurements without measuring object ple-
ase refer to chapter 12.2.2.
12.6 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Conguration
TodecodetheUARTBUSitisnecessarytorstdetermine
which channel will be connected to the data line. This set-
ting 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
Fig. 12.12: SPI data trigger menu
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. 12.13: 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.
If the option R&S®HOO11 resp. the voucher R&S®HV111 is ins-
talled, it it only possible to select analog channels as source. If
the option R&S®HOO10 resp. the voucher R&S®HV110 is installed,
both analog and digital channels are available as source.