Serial bus analysis
R&S
®
RTA4000
261
User Manual 1335.7898.02 ─ 08
●
Slave Select or Chip Select line (SS or CS)
●
Master data output, slave data input (MOSI or SDI)
●
Master data input, slave data output (MISO or SDO)
When the master generates a clock and selects a slave device, data may be transfer-
red in either or both directions simultaneously.
Figure 13-3: Simple configuration of SPI bus
The data bits of a message are grouped by following criteria:
●
A word contains a number of successive bits. The word length is defined in the pro-
tocol configuration.
●
A frame contains a number of successive words, at least one word.
For SPI buses, the R&S
RTA4000 provides the following trigger possibilities:
●
On frame start
●
On frame end
●
On a specified bit in the message
●
On a serial pattern at a specified position
13.2.2
SPI configuration
The correct setup of the protocol parameters and the threshold is the condition for
decoding the signal.
To set up and decode an SPI signal (with or without CS)
1. Press the [Protocol] key in the Analysis area of the front panel.
2. Select the bus that you want to use: B1, B2, B3 or B4.
3. Select the "Bus Type" = "SPI (no CS)" or "SPI (with CS)".
4. Select "Configuration".
5. Select the sources of the signal lines, the channels to which the lines are connec-
ted.
6. Set the threshold. Use one of the following methods:
● Tap "Find Threshold". The instrument evaluates the signal and sets the thresh-
old.
● Enter the threshold value in the numeric field.
7. Set the other signal parameters according to the signal characteristics. For details
on settings, see
SPI bus (option R&S
RTA-K1)
