1. General SPI Communication:

️· Mode Activation: SPI mode is enabled when the DMS (Diagnostic Mode Select) pin reaches 5V.
️· Purpose: Used for diagnostics, identification, and version information.

2. Device Identification and Version Information

️· RD_IDENT Instruction: Reads the device ID (fixed at 10100010).
️· RD_VERSION Instruction: Reads the version number composed of:
- SWR (Software Release): Upper 4 bits (currently all zeros)
- MSR (Mask Set Revision): Lower 4 bits (incremented with hardware changes)

3. Diagnostic Register (DIA_REG):

️· Purpose: Provides status information about the output stages (OUT1, OUT2).
️· Reset: Cleared upon:
- Rising edge of the CSN signal after RD_DIA instruction (if correct number of SCK pulses).
- DMS exceeding 5V (after under-voltage condition).
- Rising edge on EN or falling edge on DIS.
️· Format (DIA_REG):
- EN/DIS: Indicates if EN = High or DIS = High. (Not Latched)
- OT: Over Temperature. (Latched)
- CurrRed: Current Reduction due to temperature. (Latched)
- CurrLim: Current Limitation. (Latched)
- DIA21, DIA20, DIA11, DIA10: Diagnostic bits for OUT1 and OUT2.
️· Failure Priority: If multiple faults are present, they are encoded according to a priority list:
1. Under Voltage
2. Short Circuit across the load
3. Other short circuits
4. Open Load

4. Open-Load Diagnosis

️· Conditions: Only possible when inactive (EN=L or DIS=H) and in SPI mode.
️· Detection: Utilizes a specific detection circuit as illustrated in Figure 9.
️· Truth Table (Table 15): Describes the diagnostic state based on the status of outputs and load conditions.

5. Diagnostic Bit Encoding (DIA21, DIA20, DIA11, DIA10)

️· The diagnostic bits give status for the outputs, including:
- Short circuit to ground
- Short circuit to VS (supply voltage)
- Open load.
- Under Voltage on Pin Vs

Important Notes & Key Terminology:

️· DMS: Diagnostic Mode Select - Input pin enabling SPI mode.
️· EN: Enable - Output enable signal.
️· DIS: Disable - Output disable signal.
️· OUT1, OUT2: Output stages.
️· SC: Short Circuit.
️· VS: Supply Voltage.
️· SCB: Short circuit to battery.
️· SCG: Short circuit to ground.
️· SWR/MSR: Software/Mask revision numbers for version control.
️· CSN: Chip Select Not (likely an SPI term).
️· SCK: Serial Clock (likely an SPI term).