Pro II: Extension and Interface Modules
Pro II-SENT-6 Rev. E
ADwin
202
ADwin-Pro II
Hardware, manual Dec. 2018
Working with SENT
Terminology
The SENT protocol works as point-to-point connection, which transfers signal
values from a sensor to a controller. A SENT message consists of 9 or 10
pulses:
– 1 calibration pulse for synchonization
– 1 nibble pulse (1 nibble = 4 bit): Status and communication, contains
amongst others 1…2 Bits of the serial message.
– 3 nibble pulses: first 12-bit value of the sensor
– 3 nibble pulses: second 12-bit value of the sensor
– 1 nibble pulse: CRC checksum of the data pulses
– optionally 1 pause pulse
The length of pulses and SENT messages is measured in clock ticks. The
clock tick can have a length of 3µs…90µs.
A serial message consists of an ID, a data value and a CRC checksum. The
sending format (standard, enhanced 1, enhanced 2) determines the number of
bits for ID and data value. Serial messages are sent distributed to several
SENT messages, only 1…2 bits per message.
Several (up to 32) serial messages form a message set. The message set is
transferred cyclically.
Detection mode
After power-up all input channels are set to detection mode, where incoming
SENT signals are being analyzed. As soon as the module detects the clock tick
and number of pulses of SENT messages, it sets the appropriate input channel
to read mode.
Alternatively, you can set the number of pulses and the clock tick of an input
channel manually via software. With setting the clock tick, the input channel is
set to read mode without further checks.
You can switch an input channel from read mode back to detection mode via
software. This can be useful after changing the SENT sensor.
Read mode
With read mode, the module evaluates the SENT signal of the input channels
continuously and provides the contained data to be read:
– Signals 1 and 2 (fast channel) and the result of the CRC check.
A possible pause pulse of the SENT signal is automatically detected.
– ID and data value of a serial message (slow channel) and the result of
the CRC check.
The following serial message formats are detected:
• short serial message format: 4-bit ID + 8-bit data value.
• enhanced serial message format:
8-bit ID + 12-bit data value or 4-bit ID + 12-bit data value.
You can either read single serial messages consecutively or a complete
message set at once. A message set contains the recently received data
value and the number of received messages for each ID.
– Only on request the module collects all data of the next SENT message
in a latch buffer, from where you can afterwards read the data set. This
ensures that all data belong to the same SENT message.
The data set contains amongst others all 8 nibbles as well as the time
when the SENT message was received.
Checking timeout
You can query whether an input channel continuously receives SENT mes-
sages or not: As long as the return value of
P2_SENT_Get_Msg_Counter
keeps changing, new SENT messages are being received on the input chan-
nel.
