L9679P datasheet(173/272 Pages) STMICROELECTRONICS

173 / 272 page

DocID029275 Rev 1

173/272

L9679P

Remote sensor interface

271

Figure 40. Manchester bit encoding

The sensor input filter time, deglitch filter, (delay until a threshold crossing is detected) can

be configured in 15 steps. Filters can be selected individually for each channel, through the

Remote Sensor Configuration Register, WSFILT bits

The received message data are stored in input data registers that are read out by the

microcontroller via the SPI interface. For PSI5, three data registers per channel are used to

store remote sensor messages received during timeslots 1, 2, and 3 respectively. Each

message. All the bits inside the register itself are simultaneously updated upon reception of

the remote sensor message to prevent partial frame data from being sampled via the SPI

interface. After the data for a given channel is read via the SPI interface, subsequent

requests for data from this channel will result in an error response.

To allow for sampling synchronization of remote sensor data with the software in the

microcontroller, the Remote sensor Interface block includes sync-pulse circuitry to signal

initiation of sampling in the remote sensor. The sync-pulse is output to the remote sensors in

the form of an increased voltage level on the RSUx pins when sampling is to be conducted.

The higher voltage level required for the sync-pulse is sourced from the SYNCBOOST

boost regulator. Pulse shaping is used to limit the slew rate of the pulses to reduce EMI.

Feedback protection is provided to prevent fault conditions on one channel from affecting

the others during sync-pulse generation. The microcontroller schedules the activation of the

sync pulses to the four channels by providing a periodic signal to the SATSYNC pin. When a

rising edge is detected on SATSYNC pin, the Remote sensor Interface block outputs sync

pulses on channels RSU0-RSU1 in sequence to reduce the average current inrush to the

remote sensors as shown in Figure 41. The voltage source in the Remote Sensor Interface

block can source and sink current and is used to discharge the bus capacitance at the end

of the sync pulse. The pull down device used to sink current is current limited.

L9679P 数据表(PDF) 173 Page - STMicroelectronics