ATSGA204A View Datasheet(PDF) - Microchip Technology
Part Name
Description
MFG CO.
'ATSGA204A' PDF : 93 Pages View PDF
ATSHA204A
Security Commands
Whenever the input data is encrypted an authorizing input MAC is always required when writing the Data
zone. This MAC is computed as follows:
SHA-256 (TempKey, Opcode, Param1, Param2, SN<8>, SN<0:1>, <25 bytes of 0’s>, PlainTextData)
Prior to locking of the OTP/Data zones, Zone<6> is used to indicate to the device whether or not the input
data is encrypted. After locking of the OTP/Data zones, Zone<6> is ignored and only SlotConfig<14>
corresponding to the slot being written is used to determine whether or not the input data is encrypted.
If data encryption is indicated, then TempKey must be valid prior to this command being called and it
must be the result of GenDig. Specifically, this means that TempKey.Valid and TempKey.GenDig must
both be set to one. Prior to data locking, any key can be used to generate TempKey. After locking, the last
slot used by GenDig for TempKey creation and stored in TempKey.SlotID must match that in
SlotConfig.WriteKey. If the slot number being written is even, then TempKey.SourceFlag must be RAND.
If the slot number is odd, then TempKey.SourceFlag must match the value in Config.CheckMacSource
corresponding to the slot.
Table 8-40. Input Parameters
Name
Opcode Write
Size
1
Notes
0x12
Param1 Zone
Bit 7:
0 = 4 bytes of date are written to the specified zone.
1 = 32 bytes of data are written to the specified zone.
1 Bit 6:
0 = Data is written in the clear.
1 = Input data must be encrypted.
Must be zero if Data/OTP zones are locked.
Bits 5-2: Must be zero.
Bits 1-0: Select among Config, OTP or Data. See Section Zone Encoding.
Param2 Address 2 Address of first word to be written within the zone. See Section Address Encoding.
Data_1 Value 4 or 32 Information to be written to the zone; may be encrypted.
Data_2 Mac
0 or 32 Message authentication code to validate address and data.
Table 8-41. Output Parameter
Name
Size Notes
Success
1 Upon successful completion, the ATSHA204A returns a value of 0x00.
© 2018 Microchip Technology Inc.
DS40002025A-page 65
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