L9788 datasheet(174/264 Pages) STMICROELECTRONICS

174 / 264 page

Stand-by memory

L9788

174/264

DS12308 Rev 4

Stand-by memory

This memory is a general purpose memory registers array for microcontroller-data which is

supposed to be saved during standby when ECU is switched off. Intention is to reduce the

number of write cycles in microcontroller-flash.

In case of standby-power-supply failure the data is no longer valid. This condition can be

detected reading flag VB_STBY_UV MSC_READ13.FRAME2[0].

As long as the standby-power-supply is valid, no data is lost.

There are 15 memory-registers which can be used for application data. The 16th register is

an address-register which cannot be used for application data.

Before writing application data into one of the memory-registers, the address of the

memory-register must be written into the address-register with the STBY_NVM_ADD_REG

command.

After setting the address a STBY_NVM_ADD_REG command can write the corresponding

array byte.

Using the STBY_NVM_ADD_REG command and thus updating the address-register is not

necessary in case the previously written address is still correct, e.g. when application writes

consecutively to the same register.

The memory-register-addresses can have values from 0 to 14. Value 15 is not used for write

commands. This means STBY_NVM_ADD_REG commands will have no effect when

writing to address 15.

The application data is written with mentioned STBY_NVM_ADD_REG command which

writes one byte (8bit) of application data into the memory-register. To write more than one

As the other registers above, the upstream reading of the registers is not done register-wise

but in blocks of four registers. MEM_REG1 … 4, MEM_REG5 … 8, MEM_REG9 … 12 and

MEM_REG13 … 15 are grouped in the four upstream blocks of Read16.

The address-register MEM_ADR_REG16 is located at the end of the memory and is the

16th register. As mentioned, it cannot be used for application data. It is the fourth byte of the

upstream Read16 and can be read back with a read command for this block.

Before upstream-reading, the register-address must be set with the

STBY_NVM_ADD_REG command. If the previously written address is already the correct

one, the STBY_NVM_ADD_REG command is not necessary.

For upstream reading of the MEM_REGx and MEM_ADR_REG16 registers, the command

RD_COMMAND16 is used. The RD_COMMAND16 command is the same for all four

upstream blocks as the block to be read is defined via the address-register. The read-

command will not only read the addressed register, but will read the complete four-byte

upstream-block which contains the addressed register.

The STBY_NVM_ADD_REG command allows to write a MEM_VALID bit (D6) that can be

set to 1 by the microcontroller to signal that the memory has been written and validated

reading back data. If standby-power-supply is removed MEM_VALID bit is reset.

L9788 Datasheet(PDF) 174 Page - STMicroelectronics

L9788 Datasheet(HTML) 174 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL