User manual

Serial Bus Analysis
R&S
®
RTB2000
199User Manual 1333.1611.02 ─ 06
12.4 UART / RS232 (Option R&S RTB-K2)
● The UART / RS232 Interface................................................................................ 199
● UART Configuration..............................................................................................199
● UART Trigger........................................................................................................ 202
● UART Decode Results .........................................................................................204
12.4.1 The UART / RS232 Interface
The Universal Asynchronous Receiver/Transmitter UART converts a word of data into
serial data, and vice versa. It is the base of many serial protocols like of RS-232. The
UART uses only one line, or two lines for transmitter and receiver.
Data transfer
The data is transmitted in symbols, also referred to as words or characters. Each sym-
bol consists of a start bit, several data bits, an optional parity bit, and one or more stop
bits. Several symbols can form a frame, or package. The end of a frame is marked by
a pause between two symbols.
[Data8]
[Parity]
Stop[Data7][Data6][Data5]
Data4Data3Data2Data1Data0
Start
Figure 12-16: Bit order in a UART word (symbol)
●
The start bit is a logic 0.
●
The stop bits and the idle state are always logic 1.
The UART protocol has no clock for synchronization. The receiver synchronizes by
means of the start and stop bits, and the bit rate that must be known to the receiver.
Trigger
The R&S RTB2000 can trigger on specified parts of UART serial signals:
●
Start bit
●
Frame start
●
A specified symbol
●
Parity errors, and breaks
●
Frame errors
●
A serial pattern at any or a specified position
12.4.2 UART Configuration
The correct setup of the protocol parameters and the threshold is the condition for
decoding the signal.
UART / RS232 (Option R&S
RTB-K2)