ATECC508A datasheet(82/109 Pages) MICROCHIP

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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 will be used for encryption. 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.

Note: KeyConfig.ReqRandom, KeyConfig.ReqAuth, and KeyConfig.AuthKey are ignored by this

command because they will have been checked by the GenDig command for the parent encrypting key.

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, then 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 three zones:

•

Configuration Zone:

The words within this zone are always readable using this command, regardless of the value of

LockConfig.

•

OTP Zone:

If the OTP zone is unlocked this command returns an error. Once locked, if OTPmode is set to a

non-zero value and the address points to either word zero or one, then the command also returns

an error; otherwise, the corresponding word within the OTP zone is returned in the clear.

•

Data Zone:

If the data zone is unlocked, this command returns an error; otherwise, the values within the

corresponding SlotConfig word 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, this command

returns an error. If IsSecret is clear and EncryptRead is clear, this command returns the desired slot

in the clear.

Partial data blocks are always zero extended to 32 bytes before being encrypted.

Table 9-45. Input Parameters

Name

Size

Notes

Opcode

READ

0x02

Param1

Zone

Bit 7:

0 = 4 Bytes are read.

1 = 32 bytes are read.

Bits 6-2: Must be zero.

Bits 1-0: Select among Configuration, OTP, or Data. See Section Zone Encoding.

Param2 Address

Address of first word to be read within the zone. See Section Address Encoding.

Data

—

Table 9-46. Output Parameter

Name

Size

Notes

Contents

4 or 32

The contents of the specified memory location.

ATECC508A

Security Commands

Datasheet Complete

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