Specifications
37
Subject to change without notice
BIT and use the universal knob for the selection of the desired
bit number.
Further trigger possibilities will become available after pres-
sing the soft menu key SER. PATTERN, a menu will open which
allows to provide for a bit offset which may exist (values from
0 to 4095 are possible). It also permits to dene the number of
bits per message (values from 1 to 32 bits are possible) and to
set each of the bits dened.
Fig. 12.9: SPI data trigger menu.
The input of the serial bit stream may be binary or hexadecimal,
this will be dened with the soft menu key PATTERN INPUT. If
binary input is selected, the individual bits can be selected with
the soft menu key SELECT BIT and the universal knob. The soft
menu key VALUE is used to dene whether the bit should be 0, 1
or X (don’t care). If hexadecimal input is selected, the soft menu
key VALUE and the universal knob are used to set the value of
each nibble (4 bits). The soft menu key NIBBLE switches from
nibble to nibble. The presently active nibble will be marked with
a green frame. All menus will be closed by pressing the MENU
OFF key three times. The oscilloscope will now trigger on the
bit stream dened.
12.7 UART/RS-232bus
The UART (Universal Asynchronous Receiver Transmitter) bus
is a general bus system and the base for many protocols. The
RS-232 protocol is one of them. It consists of a frame with a
start bit, 5 to 9 data bits, a parity bit and a stop bit. The stop
bit can assume the nominal length of a bit, 1.5 times or twice
that length.
12.8 UART/RS-232busdenition
In order to decode the UART bus, it is rst necessary to dene
which logic channel shall be connected to the data line. Open
the bus menu, select the bus type UART and then press the
soft menu key CONFIGURATION. A menu will open, press
its top soft menu key DATA SOURCE and use the universal
knob to select the logic channel. The soft menu key ACTIVE
alternates between high and low, the selection is marked by
a blue background (for RS-232 select low). The key SYMBOL
SIZE and the universal knob are used to select 5 to 9 bits. The
key parity allows to select no, even or odd. The last soft menu
item on page 1 denes the length of the stop bit as nominal,
1.5 times or twice.
Serial bus analysis
Fig. 12.10: Page 1 of the UART bus denition menu.
On page 2 of the denition menu the bit rate can be chosen.
Fig. 12.11: Page 2 of the UART bus denition menu
After pressing the soft menu key BIT RATE the universal
knob is used to select the standard symbol rates from 300 to
115,200 symbols per second. If a different symbol rate should
be required, press the soft menu key USER and use the uni-
versal knob or the numerical input to enter the desired value.
The last setting to be performed is the dead time between
the last stop bit and the next start bit. Press the soft menu
key IDLE TIME and use the universal knob or the numerical
input for entering.
12.9 UART/RS-232bustriggering
Press the key TYPE in the TRIGGER area of the front panel for
setting the trigger conditions, then press the soft menu key
SERIAL BUSES. Subsequently press the key SOURCE in the
TRIGGER area and select the UART bus. (It will only be available
if it was previously dened.) Then press the key FILTER in the
TRIGGER area, all possible trigger options will be presented. Go
to page 1 of the trigger menu for setting the trigger condition:
STARTBIT, FRAME START, the N-th SYMBOL or a special date
are offered. In order to enter a date, select the soft menu key
DATA, a menu will open in which the desired settings can be
performed.
The soft menu key SYMBOL OFFSET and the universal knob are
used to select a number of symbols from 0 to 4095 following
the start bit which shall be ignored. The number of symbols