Protocol analysis
R&S
®
RTO6
667User Manual 1801.6687.02 ─ 05
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Long frame: it varies in length according to the frame transfer method. The PTYPE
field is only used for the polling method.
The long frame is used to transfer large amount of data.
Figure 13-21: CXPI long frame
During measurements further type of frames may also occur: PTYPE only, PID only
and PTYPE + PID only.
Frame fields
The dif
ferent frames may contain the following fields:
●
PID: consists of a frame identifier (7 bits) and one parity bit.
●
Protected TYPE (PTYPE): a special PID field with a frame identifier of 00 (hex)
and a parity of 1. It is used only in the polling method.
●
Frame information: it consists of the following fields:
– Data Length Code (DLC): 4 bits that indicate the length of the data byte of a
normal frame.
– Network Management (NM): 2 bits indicating if the frame is in wakeup or
sleep mode.
– Counter (CT): 2 bits indicating the continuity of the frame.
– extension DLC: 1 byte that is added to the frame information for long frames.
It indicates the length of the data byte field of a long frame.
●
Data byte: the length of the data byte field depends on the frame type. It contains
the actual information of the frame.
●
Cyclic Redundancy Check (CRC): 1 byte for normal and sleep frames and 2
bytes for long frames. CRC errors can be detected to check if the received data is
correct.
13.11.2 CXPI configuration
13.11.2.1 CXPI configuration settings
Access: [Bus] key > "Setup" tab > "Protocol" = "CXPI"
Make sure that the tab of the correct serial bus is selected.
CXPI (option R&S RT
O6-K520)
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