ATECC508A datasheet(58/109 Pages) MICROCHIP

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Command

Opcode Description

Typ. Exec.

Time(1)

Max. Exec.

Time(2)

Unit

SHA

0x47

Computes a SHA-256 or HMAC digest for general

purpose use by the system.

UpdateExtra

0x20

Update bytes 84 or 85 within the Configuration zone after

the Configuration zone is locked.

Verify

0x45

ECDSA verify calculation.

Write

0x12

Write 4 or 32 bytes to the device, with or without

authentication and encryption.

Note:

Typical execution times are representative of the duration to execute the command assuming no

error conditions, fastest mode setting, and favorable environmental conditions. For best

performance, delay for this interval and then start polling to determine actual command completion.

Maximum execution times are representative of the longest duration of a successful command

execution under the worst case statistical and environmental conditions. Some internal modes,

such as limited use and others will cause the delays to be as much as 50 ms longer. In most but not

all cases, failing commands will return relatively quickly, often well before the typical execution time.

9.1.4

Address Encoding

The Read and Write commands include a single 16 bit address in Param2, which indicates the memory

location to be accessed. In all cases, data is accessed on 4 byte word boundaries. The word address can

be created by taking the byte address and dropping the least significant two bits.

The Read and Write commands support either 4 or 32 byte accesses. When 32 bytes are being

accessed, the offset (i.e. the least significant three bits of the word address) must be present in the

parameter, but their value in the parameter is ignored, and the operation proceeds assuming they are

zero (i.e. all 32 byte accesses are block aligned).

Table 9-5. Address Encoding for Config and OTP Zones (Param2)

Zone

Byte 1

Byte 0

Unused

Block

Offset

Config

Bits 7-0

Bits 7-5

Bits 4-3

Bits 2-0

OTP

Bits 7-0

Bits 7-4

Bit 3

Bits 2-0

Table 9-6. Address Encoding for Data Zone (Param2)

Zone

Byte 1

Byte 0

Unused

Block

Unused

Slot

Offset

Data Slots 0 – 7

Bits 7-1

Bit 0

Bit 7

Bits 6-3

Bits 2-0

Data Slot 8

Bits 7-4

Bits 3-0

Bit 7

Bits 6-3

Bits 2-0

Data Slots 9 – 15

Bits 7-2

Bits 1-0

Bit 7

Bits 6-3

Bits 2-0

Within each zone, there are various access restrictions as noted in the table below:

ATECC508A

Security Commands

Datasheet Complete

DS20005927A-page 58

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