ATSGA204A View Datasheet(PDF) - Microchip Technology
Part Name
Description
MFG CO.
'ATSGA204A' PDF : 93 Pages View PDF
ATSHA204A
Security Commands
Table 8-39. Output Parameter
Name Size Notes
Success
1
If the memory byte was updated, this command returns a value of 0x00; otherwise, it returns an
Execution error.
8.5.18
Write Command
The Write command writes either a one 4-byte word or an 8-word block of 32 bytes to one of the
EEPROM zones upon the device. Depending on the value of the WriteConfig byte for this slot the data
may be required to be encrypted by the system prior to being sent to the device.
The following restrictions apply to writes within zones using this command:
• Data Zone: If the Configuration zone is locked and the Data zone is unlocked, then all bytes in all
zones can be written with either plain text or encrypted data using 32 byte writes. After the Data
zone is locked, the values within the WriteConfig bytes control access to the data slots. If the
WriteConfig bits for this slot are set to “always”, then the input data should be passed to the device
in the clear. If SlotConfig<14> is set to one, the input data should be encrypted and an input MAC
calculated.
• Configuration Zone: If the Configuration zone is locked or Zone<6> is set, then this command
returns an error; otherwise the bytes are written as requested. Any attempt to write any byte for
which Writes are permanently prohibited (per Section EEPROM Data Zone) results in a command
error with no modifications to the EEPROM.
• OTP Zone: If the OTP zone is unlocked, then all bytes can be written with this command. If the
OTP zone is locked and the OTPmode byte is read-only or legacy, then this command returns an
error; otherwise, OTP mode should be consumption and this command sets to zero those bits in
the OTP zone that correspond to the zero bits in the input parameter value. When the OTP zone is
locked, encrypted writes to it are never permitted regardless of OTPmode.
Four byte writes are only permitted in the Data and OTP zones if all four of the following conditions are
met:
• SlotConfig.IsSecret must be zero.
• SlotConfig.WriteConfig must be “always.”
• The input data must not be encrypted.
• The Data/OTP zones must be locked.
Four byte writes return an error under all other circumstances.
The least significant three bits of Param2, Address<2:0>, indicate the word within the block, or are
ignored if an entire 32 byte block is being written. Address<6:3> contains the slot number for writes to the
Data zone, or the block number for the Configuration and OTP zones. Address values beyond the size of
the specified zone result in the command returning an error.
Any attempt to write the OTP and/or Data zones prior to the configuration section being locked results in
the device returning an error code.
8.5.18.1
Input Data Encryption
The input data may be encrypted to prevent snooping on the bus during personalization or system
operation. The system should encrypt the data by XORing the plain text with the current value in
TempKey. Upon receipt, the device will XOR the input data with TempKey to restore the plain text prior to
writing to the EEPROM.
© 2018 Microchip Technology Inc.
DS40002025A-page 64
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