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AN2014

Software considerations

Figure 35. MICROWIRE data polling algorithm

1. There is no difference in the data polling process if chip is deselected between 2 ready/busy checks.

2. It is strongly recommended not to operate the Clock during the data polling sequence because as soon as

the chip is ready, the logic will start to decode incoming bits.

5.3

Write protection

5.3.1

Software write protection

Use the software write protection features to protect sensitive data items:

•

I²C products have no software write protection.

•

In SPI products, 2 non-volatile Status Register bits (BP0, BP1) are dedicated to the

software write protection. The upper quarter, the upper half or the whole memory array

can be set as Read-Only.

•

In 1 Kbit to 4 Kbit M93Sxxx MICROWIRE products the amount of data to protect is

directly set by a user instruction. The selected area becomes a Read-Only memory.

Data items like trace codes, identification codes, manufacturing configurations, default

parameters and all sensitive data in general, can be software protected against corruption

during field service. Software protection bits are non volatile bits and therefore offer the

same cycling and data retention performances than the EEPROM memory bits.

Ai11081

Write in Progress

Select (S=1)

Deselect (S=0)

Ready/Busy

on Q pin

Q level

Deselect (S=0)

Ready for new command

Low

(1)

High

(2)

AN2014 데이터시트(PDF) 41 Page - STMicroelectronics