ATSHA204A-XHCZ-T 查看數據表（PDF） - Microchip Technology
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ATSHA204A-XHCZ-T Datasheet PDF : 93 Pages
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ATSHA204A
Device Organization
Table 2-9. Configuration Zone Locking
Lock State
LockConfig == 0x55 (unlocked)
LockConfig != 0x55 (locked)
Read Access
Read
Read
Write Access
Write
<never>
2.1.4.2
Data and OTP Zone Locking
Throughout this document, if LockValue is 0x55, then both the Data and OTP zones are said to be
unlocked; otherwise they are locked.
There is neither read nor write access to the Data and OTP zones prior to locking of the Configuration
zone.
Table 2-10. Data and OTP Zone Access Restrictions
Lock State
Read Access
Write Access
LockValue == 0x55 (unlocked)
LockValue != 0x55 (locked)
<never>
Read(1)
Write
Write(1)
2.1.4.3
Note:
1. Based on Slot Configuration for a given slot.
OTP Zone Locking
Reads and writes of the OTP zone depend upon the state of the LockConfig, LockValue and OTP mode
bytes in the Configuration zone.
2.2
2.2.1
Static RAM (SRAM)
The device includes an SRAM array that is used to store the input command or output result,
intermediate computation values and/or an ephemeral key. The entire contents of this memory are always
invalidated whenever the device goes into sleep mode or the power is removed. The ephemeral key is
named TempKey and can be used as an input to the MAC, HMAC, CheckMac, GenDig and DeriveKey
commands. It is also used as the Data protection (Encryption or Decryption) key by the Read and Write
commands. See Section TempKey.
TempKey
TempKey is a storage register in the SRAM array that can be used to store an ephemeral result value
from the Nonce, GenDig, CheckMac, or SHA commands. The contents of this register can never be read
from the device (although the device itself can read and use the contents internally).
This register contains the elements shown in the table below.
Table 2-11. TempKey Storage Register
Name
TempKey
Bit Length Description
256
(32-bytes)
Nonce (from Nonce command) or Digest (from GenDig command).
SlotID
If TempKey was generated by GenDig (see the GenData and CheckFlag bits), these
4
bits indicate which key was used in its computation. The four bits represent one of the
slots of the Data zone.
© 2018 Microchip Technology Inc.
DS40002025A-page 17
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