User manual
51
Serial Bus Analysis
Press the MENU OFF button several times to close all me-
nus, and the oscilloscope will trigger on the set address
and data. For measurements without measuring object
please refer to chapter 12.2.2.
12.5 SPI / SSPI BUS
The Serial Peripheral Interface SPI is used to communicate
with slow peripheral devices, in particular for the transfer
of data streams. The SPI bus was developed by Motorola
(today known as Freescale); however, it has not been for-
mally standardized. Generally, this is a bus with clock and
data lines and a select line (3-wire). If only one master and
one slave are present, the select line may be deleted. This
type of line is also called SSPI (Simple SPI) (2-wire). A SPI
BUS has the following properties:
❙ Master-slave communication
❙ No instrument addressing
❙ Noacknowledgetoconrmdatareception
❙ 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 si-
multaneously in both directions (only available with
R&S®HOO10/R&S®HV110).
12.5.1 SPI/SSPIBUSKonguration
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
For SPI/SSPI BUS trigger and decoding you need the R&S®HOO10
resp. R&S®HOO11 option or the upgrade voucher R&S®HV110
resp. R&S®HV111.
The address decoding is a 7-bit value. The 8th bit of write-read is
decoded in color, not in the HEX value of the address.
Fig.12.9:SimplecongurationofaSPIBUS
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. With 3-wire SPI the CS (chip select) has to be
connected to the external trigger input. The level can be set in
the BUS conguration menu via EXTERNAL LEVEL.
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)
❙ 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-
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 but-
If the option R&S®HOO11 resp. the voucher R&S®HV111 is in-
stalled, it it only possible to select analog channels as source.
If the option R&S®HOO10 resp. the voucher R&S®HV110 is ins-
talled, both analog and digital channels are available as source.
Fig.12.10:MenuforthedenitionofaSPIbus