ATSHA204A datasheet(8/93 Pages) MICROCHIP

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Device Organization

The device contains the following memory blocks:

•

EEPROM

•

SRAM

2.1

EEPROM Organization

The EEPROM contains a total of 664-bytes (5312-bits) and is divided into the following zones:

Table 2-1. ATSHA204A Zones

Zone

Description

Nomenclature

Data

Zone of 512 bytes (4.0 kb) split into 16 general purpose read-only or

read/write memory slots of 32 bytes (256 bits) each that can be

used to store keys, calibration data, model number, or other

information, typically that relate to the item to which the ATSHA204A

device is attached. Access policy of each data slot is determined by

the values programmed into the corresponding configuration values.

However, the policies become effective upon setting the LockValue

byte only.

Slot<YY> = The entire

contents stored in Slot YY

of the Data zone.

Configuration

Zone of 88 bytes (704 bits) EEPROM that contains the serial

number and other ID information, as well as, access the permission

information for each slot of the data memory. The values

programmed into the configuration zone determine the access

policy of how each data slot responds. The configuration zone can

be modified until it has been locked (LockConfig set to !=0x55).

In order to enable the access policies, the LockValue byte must be

set. (See section above)

SN<a:b> = A range of

bytes within a field of the

Configuration zone.

One Time

Programmable

(OTP)

Zone of 64 bytes (512 bits) of OTP bits. Prior to locking the

OTPzone, the bits may be freely written using the standard Write

command. The OTP zone can be used to store read-only data or

one-way fuse type consumption logging information.

OTP<bb> = A byte within

the OTP zone, while

OTP<aa:bb> indicates a

range of bytes.

Terms discussed within this document have the following meanings:

Table 2-2. Document Terms

Term

Meaning

Block

A single 256-bit (32-byte) area of a particular memory zone. Industry SHA-256 documentation uses the

term “block” to indicate a 512-bit section of the message input. In addition, the I/O section of this

document uses the term “block” to indicate a variable-length aggregate element transferred between

the system and the device.

Slot

For the data zone the terms “Block” and “Slot” can be used interchangeably. For the OTP and Config

zone there are multiple blocks of 32 Bytes each.

param<b> Indicates one bit of parameter or byte field.

SRAM

Contains input and output buffers, as well as state storage locations. See Section Static RAM (SRAM)

ATSHA204A

Device Organization

DS40002025A-page 8

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