at88sc0104c ATMEL Corporation, at88sc0104c Datasheet - Page 22

• Manufacturer Part Number: at88sc0104c
• Description: Cryptomemory Specification For Standard Mode Of Operation
• Manufacturer: ATMEL Corporation

5.3.9.2
5.3.9.3
5.3.9.4
5.3.9.5
5.3.9.6
5.3.10
5.3.10.1
5.3.10.2
18
AT88SC0104/0204/0404/0808/1616/3216/6416/12816/25616C
Password/Key Registers
AM(1:0) – Authentication mode
ER – Encryption Required
WLM – Write Lock Mode
MDF – Modify Forbidden
PGO – Program Only
AK(1:0) – Authentication Key
POK(1:0) – Program Only Key
When PM = “11”, the user zone under protection requires no password. When PM = “10”, the
zone requires Write Password verification for writing and reading is free. When PM = “01” or
“00”, reading requires the read password verification and writing requires write password verifi-
cation. However, proper verification of the Write Password also grants read access. The
password set required is specified by PW(3:0) in the corresponding Passwords/Keys Register
(see following section). Verification of the Write password also allows modification of the read
and the write passwords.
The AM bits allow configuration of the authentication modes and only available under the
authentication mode of operation.
The use of the ER bit is applicable in the encryption mode of operation.
Asserting this bit (WLM = “0”) divides the user zone into 8-byte pages. The first byte of each
page becomes the Write Lock Byte and defines the locked/unlocked status for each byte in the
page. Write access is forbidden to a byte if its associated bit in the Write Lock Byte is set to “0”.
Bit 7 controls byte 7; bit 6 controls byte 6, etc. Setting bit 0 to “0” locks the Write Lock Byte itself.
Enabling Write Lock Mode limits write operations to one byte at a time.
Asserting this bit (MDF = “0”) renders the user zone read-only at all times. The user zone must,
therefore, be programmed before setting this bit to “0”
Asserting this bit (PGO = “0”) allows changing of data within the user zone under protection from
“1” to “0” and never from “0” to “1”.
Four, eight or sixteen 8-bit Password/Key registers receive definition during device personaliza-
tion. Each Password/Key register works in conjunction with a corresponding Access register to
define the security settings of each zone. The values programmed have an immediate affect on
the logic of the device. The default value is “1” for each bit. Bit 3 is reserved and should be left
as value “1.”
Table 5-5.
The AK bits are applicable under the authentication mode of operation.
The POK bits are applicable under the authentication mode of operation.
Bit 7
AK1
Bit 6
AK0
Password/Key Register Definition
POK1
Bit 5
POK0
Bit4
Bit 3
Res
PW2
Bit 2
PW1
Bit 1
5210A–SMIC–04/07
PW0
Bit 0