Protocol analysis
R&S
®
RTO6
666
User Manual 1801.6687.02 ─ 05
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SEARch:RESult:SENT:FRAMe<m>:TYPE?
13.11
CXPI (option R&S
RTO6-K520)
The Clock Extension Peripheral Interface (CXPI) protocol defines a communication
standard for the vehicles electric system. It is developed by the Society of Automotive
Engineers of Japan, Inc. (JSAE).
13.11.1
The CXPI protocol
This chapter provides an overview of the protocol characteristics, frame types and
frame fields.
CXPI characteristics
Main characteristics of CXPI are:
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Carrier Sense Multiple Access (CSMA) and Collision Resolution (CR)
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The master sends pulse width modulated clock (PWMC)
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Support of the sleep/wake function to reduce power consumption
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Support of two methods for frame transfer management, the event trigger method
and the polling method.
The event trigger method can be used when the focus is placed on the responsive-
ness of the slave node communication. The polling method puts the focus on the
communication periodicity.
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Maximum baud rate of 20kbit/s
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Up to 16 nodes connected to a communication bus
Frame types
The CXPI protocol defines three types of frames:
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Normal frame
: it varies in length according to the frame transfer method. The
PTYPE field is only used for the polling method.
The normal frame is used to transfer compact data.
Figure 13-19: CXPI normal frame
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Sleep frame
: it has a fixed length and fixed values for the PID and data fields. It is
sent by the master node to command the slave nods to change into sleep state.
Figure 13-20: CXPI sleep frame
CXPI (option R&S
RTO6-K520)
