ATECC508A datasheet(87/109 Pages) MICROCHIP

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•

If Mode<1> is set, The command implements a fast decrement of the limited use counters which

may be associated with a particular key.

–

If the slot indicated by the “NewValue” param does not contain a key for which limited use is

implemented or enabled, then the command returns silently without taking any action.

–

If the indicated slot contains a limited use key, which does not have any uses remaining, then

the command returns an error.

•

If the mode parameter indicates UserExtra at address 84:

–

If the current value in UserExtra (byte 84 of configuration zone) is zero, then UpdateExtra

writes this byte with the LSB of NewValue and returns success.

–

If the current value in UserExtra is non-zero, then the command returns an execution error.

•

If the mode parameter indicates Selector at address 85:

–

If the SelectorMode (ChipMode.Bit0 of the device mode within the configuration zone) is set

to one and Selector (byte 85 of the configuration zone) is non-zero, then this command will

Write Selector with the LSB of NewValue and return success.

–

If SelectorMode is cleared, indicating that no check of the current Selector should be made,

then this command always updates Selector and always succeeds.

Table 9-52. Input Parameters

Name

Size

Notes

Opcode UpdateExtra

0x20

Param1

Mode

Bits 7–2: Must be zero.

Bit 1:

0 = Update Config byte 84 or 85.

1 = Ignore bit 0, and decrement the limited use counter associated with

the key in slot NewValue

Bit 0:

0 = Update Config byte 84.

1 = Update Config byte 85.

Param2

NewValue

LSB:

Value to optionally be written to location 84 or 85 in Configuration zone.

MSB: Must be 0x00.

Data

—

Table 9-53. Output Parameter

Name

Size

Notes

Success

If the memory byte was updated, this command returns a value of 0x00; otherwise, it returns an

execution error.

9.20

Verify Command

The Verify command takes an ECDSA <R,S> signature and verifies that it is correctly generated from a

given message and public key. In all cases, the signature is an input to the command.

The Verify command can operate in four different modes:

ATECC508A

Security Commands

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