VNF1248F datasheet(38/79 Pages) STMICROELECTRONICS

38 / 79 page

The default configuration is available in fail-safe/locked states for almost all parameters, with the following

exceptions:

•

BYPASS_CTL_DEF: it is used for setting bypass switch status in fail-safe and standby states, when

NVM_DEF_CFG_EN is set (not in locked state).

•

FS_MODE_DEF: it is used for setting output control configuration in fail-safe state only (not in locked

state).

•

DIN_CTRL_EN, DIN_CTRL_OPT: they are used to configure DIN use and its combination with software

control in the locked state only (not in the fail-safe state).

10.1.1

NVM default configuration and output control mode in fail-safe

Considering the three different operation modes available in fail-safe, the availability of default configuration is

meaningful in the cases shown by the following table:

Table 31. Device and output configuration options

Output control mode

RAM-based configuration

FS_DEF_CFG_EN = 0

NVM-based configuration

FS_DEF_CFG_EN = 1

OUTPUT DIN CONTROLLED

(FS_MODE = 00/01)

YES

OUTPUT LAST STATUS

(FS_MODE = 10)

YES

OUTPUT OFF

(FS_MODE = 11)

YES

10.1.2

NVM default configuration and RAM registers in fail-safe

If default configuration into NVM is enabled, by NVM_DEF_CFG_EN dedicated bit in NVM, and FS_MODE =

00/01 (DIN control on output), user write access to RAM registers is allowed in the fail-safe state, especially for

programming configuration fields of Table 30. NVM mapped configuration parameters, to let the preparing device

configuration for the unlocked state; those settings are stored but not effective until the fail-safe to unlocked

transition occurs.

User write is not effective for the register field NVM_DEF_CFG_EN that is used only for related NVM bit setting

during the NVM programming phase.

With FS_MODE = 10/11, all RAM registers are locked to write access, except for the following control bits:

•

CR#→ EN

•

CR#1→ GOSTBY

•

CR#1→ FS_CFG_UPLOAD (not effective with NVM_DEF_CFG_EN = ‘0’)

•

CR#3→ UNLOCK

10.1.3

NVM default configuration and RAM registers in locked

If default configuration into NVM is enabled, (NVM_DEF_CFG_EN = ‘1’), in the locked state the device is

configured with fixed configuration parameters stored into NVM; user writes to RAM configuration registers fields

of Table 30. NVM mapped configuration parameters is allowed, considering those settings are stored but is not

effective until the locked to unlocked transition occurs. The other RAM control register fields not belonging to the

NVM default configuration, mainly dedicated to output control, features activation triggering and specific device

controls, is write accessible, giving the freedom to have full output control with fixed parameter settings. These

registers fields are reported in the Table 32:

VNF1248F

Non-volatile memory (NVM) customer programming

DS14109 - Rev 7

page 38/79

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