ATSHA204 Datasheet, PDF (35/65 Pages) ATMEL Corporation – Atmel CryptoAuthentication

8.1.4
Address Encoding
The Read and Write commands include a single address in Param2 that indicates the memory to be accessed. All Reads and
Writes are in units of four bytes (one word). The most-significant byte of a legal ATSHA204 address is always zero. All unused
address bits should always be set to zero. The least-significant bits in the address describe the offset to the first word to be
accessed within the block/slot, while the upper bits specify the block/slot number per the table below:
Table 8-5. Address Encoding (Param2)
Zone
Config
OTP
Data
Byte 1
Unused
Bits 0  7
Bits 0  7
Bits 0  7
Byte 0
Unused
Bits 5  7
Bits 4  7
Bit 7
Block/Slot
Bits 3  4
Bit 3
Bits 3  6
Offset
Bits 0  2
Bits 0  2
Bits 0  2
Within each zone, there are various access restrictions per the table below:
Table 8-6. Legal Block/slot Values
Zone
Config
OTP
Data
Legal Block/Slot
(inclusive)
Notes
0-2
Addresses below 16 (block 0, offset 16) and above 87 (block 2, offset 23) can never be written.
Addresses above 87 can never be read. Both 4- and 32-byte reads/writes are permitted
0-1
When OTPmode is read-only, all offsets in both blocks are available to use with 4- or 32-byte
reads.
If OTPmode is consumption, then writes are also permitted to all offsets.
See Section 2.1.3 if OTPmode is Legacy.
0-15
All offsets in all slots available for both read and write.
4-byte access permitted on a particular slot only if SlotConfig.IsSecret is zero.
In the table below, “Byte Address” is the byte address within the data zone for the first byte in the respective slot. Because all
Reads and Writes with the ATSHA204 are performed on a word (4-byte or 32-bit) basis, the word address in the table below
should be used for the address parameter passed to the Read and Write commands.
Table 8-7. Data Zone Slots
Slot #
0
1
2
3
4
5
6
7
Byte Address
(Hex)
0x0000
0x0020
0x0040
0x0060
0x0080
0x00A0
0x00C0
0x00E0
Word Address
(Hex)
0x0000
0x0008
0x0010
0x0018
0x0020
0x0028
0x0030
0x0038
Slot #
8
9
10
11
12
13
14
15
Byte Address
(Hex)
0x0100
0x0120
0x0140
0x0160
0x0180
0x01A0
0x01C0
0x01E0
Word Address
(Hex)
0x0040
0x0048
0x0050
0x0058
0x0060
0x0068
0x0070
0x007F
Atmel ATSHA204 [DATASHEET] 35
8740D−CRYPTO−3/12