L9963E datasheet(21/184 Pages) STMICROELECTRONICS

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Table 12. Port L configuration determination

Electrical condition

Latched when

Configuration

Wake up source

SPIEN = 1

Upon VCOM_UV

release

Port L configured as SPI. Master Unit. SPIEN

must be connected to VCOM

SPI wake up logic

SPIEN = 0 (default

condition if pin is left

floating)

Upon VCOM_UV

release

Port L configured as isolated SPI. Slave Unit.

SPIEN must be connected to AGND

ISOL wake up

comparator

In case the first power up fails and L9963E comes back to Sleep state without having latched the PORT L

operating mode, both wake up sources will be kept active in order to allow subsequent power up trigger in both

operating configurations.

When first power up completes successfully, only the wake up source related to the units with SPIEN = 1 are

Master units of the daisy chain. A Master Unit differs from the Slave ones (SPIEN = 0) because:

•

It manages the asynchronicity between SPI CLK and the programmable bit-rate on the isolated line;

•

It exploits an internal buffer to store answers received from the slaves on ISOH port;

•

It implements timeout mechanisms and frame error checks described in Section 4.2.4.4 Special frames;

•

It forwards commands only if they are addressing Slave units. Any command addressed to the Master unit is

not propagated on the ISOH port;

•

In case Master Unit has port H disabled (isotx_en_h = 0), trying to communicate with a Slave unit will return

the corresponding Master’s register content;

Interaction between Port H and Port L is managed by L9963E. The IC is capable of converting analog signals

incoming on the isolated twisted pair to digital signals suitable for SPI, and viceversa. Passing a signal through

a single unit takes a single pulse period (2*TBIT_HIGH_LOW_FAST or 2*TBIT_HIGH_LOW_SLOW, depending on the

programmed operating frequency), which can be used to account for the insertion delay of an L9963E in the daisy

chain.

4.2.1.1

Wake up via communications interface

To wake up the device from low power modes, any communication frame in low frequency (FISO_SLOW) can be

sent:

•

If port L is configured in SPI mode, a sequence of at least 37 clock pulses on SCK line with active low chip

select NCS will wake up the device. Pulses must be received within TWAKEUP_TIMEOUT_SPI timeout starting

from the NCS assertion. Before sending the wake up frame, NCS must have been set high for at least

TWAKEUP_NCS_HIGH.

•

If port L is configured in isolated SPI mode, a sequence of at least 37 differential pulses on ISOLP/ISOLM

pins, whose minimum duration is TDET_MIN_WU and whose amplitude is greater than Wakeup_thr will wake

up the device. Pulses must be received within TWAKEUP_TIMEOUT_ISO timeout starting from the first valid

pulse.

•

If port H is enabled, a sequence of at least 37 differential pulses, whose minimum duration is TDET_MIN_WU

and whose amplitude is greater than Wakeup_thr will wake up the device. Pulses must be received within

TWAKEUP_TIMEOUT_ISO timeout starting from the first valid pulse.

Note:

Depending on pulses re-synchronization uncertainty with the internal standby oscillator, the wake up event may

occur even if COM pulses are less than 37 (min. number of pulses in the best case is 8). However, 37 pulses will

always guarantee a correct wake up.

In case first power up fails and SPIEN value is not correctly latched, port L will listen to both wake up sources,

until a correct power up sequence is achieved and port L configuration is determined.

4.2.2

Serial Peripheral Interface (SPI)

The SPI pinout is listed in the following table:

Table 13. L9963E pin used as SPI

L9963E pin

SPI function

Configuration

ISOLp_SDI

Serial Data Input (SDI)

Digital input

L9963E

Serial communication interface

DS13636 - Rev 4

page 21/184

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