ATSGA204A View Datasheet(PDF) - Microchip Technology
Part Name
Description
MFG CO.
'ATSGA204A' PDF : 93 Pages View PDF
ATSHA204A
Security Commands
Param2
Data
Name
Zero
—
Size Notes
2 Must be 0x0000.
0—
Table 8-31. Output Parameter
Name
Size
RandOut
32
Notes
The output of the RNG.
Table 8-32. Mode Encoding
Bits Meaning
7 – 1 Must be zero.
0
0
=
Automatically update EEPROM seed only if necessary prior to random number generation.
Recommended for highest security.
1 = Generate a random number using existing EEPROM seed; do not update EEPROM seed.
8.5.15
Read Command
The Read command reads words (one 4-byte word or an 8-word block of 32 bytes) from one of the
memory zones of the device. The data may optionally be encrypted before being returned to the system.
See Section EEPROM Data Zone for Data zone byte and word addressing information.
If reading from a slot in which SlotConfig.EncryptRead is set, the GenDig command must have been run
prior to the execution of this command to generate the key that is used for encryption. If the slot number
is even, or if the CheckMacSource bit corresponding to this slot is zero, then the input nonce to GenDig
must have been a random number. Finally, the key specified in SlotConfig.ReadKey must have been
used in the GenDig calculation.
The device encrypts data to be read by XORing each byte read from the EEPROM with the
corresponding byte from TempKey. Encrypted reads of the Configuration and/or OTP zones are not
permitted.
The byte addresses to be read should be divided by four (drop the least-significant two bits) before being
passed to the device. If 32 bytes are being read, the least-significant three bits of the input address are
ignored. Addresses beyond the end of the specified zone result in an error.
The following restrictions apply to the following three zones:
• Data
If the Data zone is unlocked, this command returns an error; otherwise, the values within the
corresponding SlotConfig word act to control access to the data slot. If SlotConfig.IsSecret is set
and a four byte read is attempted, the device returns an error. If EncryptRead is set, this command
encrypts the data as specified above. If IsSecret is set and EncryptRead is clear, then this
command returns an error. If IsSecret is clear and EncryptRead is clear, then this command returns
the desired slot in the clear.
• Configuration
The words within this zone are always readable using this command, regardless of the value of
LockConfig.
© 2018 Microchip Technology Inc.
DS40002025A-page 60
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