Protocol analysis
R&S
®
RTO6
636
User Manual 1801.6687.02 ─ 05
The format of a SENT message frame has a fixed pulse order and a transmitter-spe-
cific clock period. The total transmission time varies depending on the clock variation of
the transmitter and the transmitted data values. The data pulses embedded in the
transmission sequence represent one or multiple data parameters to be communica-
ted. The last pulses in a message frame are the CRC check pulse, allowing the
receiver to perform a number of diagnostic tests, and an optional pause pulse.
A SENT transmission starts without a request from the receiver. Consecutive sequen-
ces are transmitted continuously after the falling edge of the last pulse.
The SENT protocol distinguishes between two channel types:
●
Fast channel:
transmits primary data, i.e. sensor readings like temperature, pres-
sure, mass air flow, throttle position.
●
Slow channel:
transmits secondary data consisting of transfer characteristics, sen-
sor ID, type, manufacturer diagnostic, etc.
The slow channel transmission provides two serial message formats
Short
and
Enhanced
for customizing the secondary data.
The data of both, the fast and the slow channels is transmitted simultaneously, by
including two bits of a slow channel message in the message frame of the fast chan-
nel. Even though it requires many fast channel messages to complete a slow channel
message, you can use this function to transmit several slow channel messages with
minimal impact on the primary sensor data and the data rate.
13.10.1.2
SENT message definitions
SENT terms
See the specific terms and definition used in SENT protocol:
●
Tick (clock tick):
basic unit of time
–
transmitter-specific nominal clock period
–
3
µs
<
clock tick
<
90
µs, with max. 20
% clock variation
●
Nibble:
minimum unit of data
–
used to transmit data
–
variable timing units between two falling edges
SENT fast channel
The SENT protocol enables you to transmit measurements of multiple sensors in one
transmission sequence with data signals of varying length. The diagram in
shows, for example, the encoding scheme for two 12-bit data signals.
SENT (option R&S
RTO6-K520)
