ATSGA204A View Datasheet(PDF) - Microchip Technology
Part Name
Description
MFG CO.
'ATSGA204A' PDF : 93 Pages View PDF
ATSHA204A
Security Commands
2. Optionally run the GenDig command to combine one or more stored EEPROM locations in the
device with the nonce. The result is stored internally in the device within tempkey. This capability
permits two or more keys to be used as part of the response generation.
3. Run this MAC command to combine the output of Step 1 (and Step 2 if desired) with an EEPROM
key to generate an output response (or digest).
Table 8-22. Input Parameters
Opcode
Param1
Name
MAC
Mode
Param2 SlotID
Size
1
1
2
Notes
0x08.
Controls which fields within the device are used in the message.
Which internal key is to be used to generate the response.
Bits 3-0 only are used to select a slot but all 16 bits are used in the
SHA-256 message.
Data
Challenge 0 or 32 Input portion of message to be digested, ignored if Mode<0> is one.
Table 8-23. Output Parameter
Name
Response
Size
32
Notes
SHA-256 digest.
The message that is hashed with the SHA-256 algorithm consists of the following information:
32 bytes
32 bytes
1 byte
1 byte
2 bytes
8 bytes
3 bytes
1 byte
4 bytes
2 bytes
2 bytes
key<SlotID> or TempKey (See table below)
Challenge or TempKey (See table below)
Opcode (Always 0x08.)
Mode
Param2
OTP<0:7> or zeros (See table below)
OTP<8:10> or zeros (See table below)
SN<8>
SN<4:7> or zeros (See table below)
SN<0:1>
SN<2:3> or zeros (See table below)
Table 8-24. Mode Encoding
Bits Meaning
7 Must be zero.
0=
6
1=
Set the bits corresponding to SN<2:3> and SN<4:7> to 0.
Include the 48 bits SN<2:3> and SN<4:7> in the message.
If Mode<4> is set, the value of this mode bit is ignored.
5 0 = Set the Corresponding 64 OTP bits to 0.
© 2018 Microchip Technology Inc.
DS40002025A-page 56
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