The Peripheral Sensor Interface is an interface for automotive sensor applications. PSI5 is an open standard based on existing sensor interfaces for peripheral airbag sensors, already proven in millions of airbag systems.

The following block diagram shows a global view of the PSI5-S interface.

Figure 1. PSI5-S block diagram

PSI5 defines a current loop based serial communication link typically used to connect airbag sensors or other peripheral devices. PSI5 provides high speed and high reliability data transfer. The PSI5-S acts as a slave on the SPB bus. The PSI5-S kernel is composed of the clock control block that is driven by the system clock frequency

fSPB

The PSI5-S consists of three main blocks that are shared between 8 channels :

  • Message Generation block that is used for preparing the transmit data

  • Message Recovery block that processes the received messages

  • Common ASC module

While the physical layer is done externally, this module manages communication with this PHY and the presentation of the data to the application. Note that there is no on chip PHY, therefore the current to voltage and voltage to sync pulse translation is done externally.

Receive data on a PSI5-S channel can be set up according to the underlying application. In particular the number of bits is configurable.

The message storage consists of a set of 3 32-bit registers for all channels: one receive data register containing the received sensor data, one timestamp register containing the 24-bit value and one additional register containing status bits.

For Synchronous Communication mode, the module can consume sync pulses from the external GTM/eGTM or generate periodic sync pulses by itself. It supports as well ECU to sensor communication by offering a 32-bit register, where messages can be set up by the CPU. All kinds of sync pulses are translated into a referring, programmable byte to be sent through ASC.

The register set of the PSI5-S module can be accessed directly by the CPU for configuration, data read out and status query.