STV2050A datasheet(63/83 Pages) STMICROELECTRONICS

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STV2050A - BOOT SEQUENCE

To initiate access to an EEPROM, the MCU must generate this code. A simple method is to

store the values in a single temporary byte TMP[7:0] and to compute each bit of the Hamming

HAM[3:0] bits as follows:

HAM[0] = TMP[4] XOR TMP[3] XOR TMP[2] XOR TMP[1] XOR TMP[0]

HAM[1] = TMP[6] XOR TMP[5] XOR TMP[4] XOR TMP[2] XOR TMP[0]

HAM[2] = TMP[7] XOR TMP[5] XOR TMP[2] XOR TMP[1]

HAM[3] = TMP[7] XOR TMP[6] XOR TMP[4] XOR TMP[3]

14.3 SECURITY OUTPUT

The POUT output can be considered as an open drain from a functional point of view, that is

to say that it can have two electrical states: high impedance or pull-down to the ground.

It can be used, for example, to force all external amplifiers to a secured biasing. Refer to

Figure "" on page 8.

The electrical status of this output is controlled by the PPL bit in the E3 register.

During normal operation it is pulled down to ground:

– if the STV2050A detects a malfunction such as a parity check error or power on reset error.

– until the power-on reset is released.

Otherwise, POUT is set to high impedance. In this case, the logical status of the POUT pin can

be read using the S02 bit in the E3 register.

15 BOOT SEQUENCE

At startup, or following a reset on pin 13, the STV2050A will:

– Immediately disable all the outputs (forced to the “zero current” value, in order to protect the

application against over-currents in the coils for example),

MSB

LSB

TMP BYTE

EEPROMadd [2:0]

ADS[1:0]

RWM [2:0]

PPL

0: Normal operation

1: High impedance

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