at88sa100s ATMEL Corporation, at88sa100s Datasheet - Page 2

• Manufacturer Part Number: at88sa100s
• Description: Battery Authentication Chip
• Manufacturer: ATMEL Corporation

1.1.
1.2.
2
Memory Resources
Sram
MemValid
Fuse
ROM
Fuse Map
The AT88SA100S chip incorporates 128 one-time fuses within the chip. Once burned, there is no way to reset the
value of a fuse. Fuses, with the exception of the manufacturing ID and serial number bits, which are initialized by
Atmel, have a value of 1 when shipped from the Atmel factory and transition to a 0 when they are burned.
Table 1.
Fuse Lock Bits These 8 fuses can be used to prevent further writing of the status fuses. Bit 0, when burned, locks
Status Fuses
AT88SA100S [Preliminary]
96
88
8
Fuse #
ROM MfrID
ROM SN
RevNum
0 – 7
87
127
95
The 128 fuses in the AT88SA100S chip are arranged in the following manner:
Fuse Lock Bits
Status Fuses
Fuse MfrID
Fuse SN
256 bits of SRAM that are used for storage of a key. The LoadSram command provides a
mechanism to securely initialize this block during personalization. This memory will retain its value
when the chip is put/goes to sleep, so long as a supply voltage in excess of V
the chip.
A single bit that tells whether or not Sram contains valid data. It’s cleared when power is lost and set
when the SRAM is loaded with a secret key.
Block of 128 fuse bits that can be read and written through the 1 wire interface. The first 8 bits are
lock bits that control burn ability on 16 bit words of the array. Fuse[88-95] are part of the
manufacturing ID values fixed by Atmel. Fuse[96-127] are part of the serial number programmed by
Atmel which is guaranteed to be unique. See Section 1.3 for more details on the Manufacturing ID
and Serial Number.
Metal mask programmed memory. Unrestricted reads are permitted on the first 64 bits of this array.
The physical ROM will be larger and will contain other information that cannot be read.
Fuse[0-15] from being modified, Bit[1] locks Fuse[16-31] and so on up through bit 5, which locks
Fuse[80-87]. Fuse[88-127] can never be modified with the BurnFuse command. Note that burning bit
0 has the effect of preventing any changes to the current value of the lock bits.
These fuses can be used to store various information which is not secret. Their value can always be
determined using the Read command. They can be individually burned using the BurnFuse
command. Two common usage models for these fuses are:
Name
2 bytes of ROM that specifies part of the manufacturing ID code. This value is assigned by Atmel
and is always the same for all chips of a particular model number. For the AT88SA100S, this
value is 0xFF FF. ROM MfrID can be read by accessing ROM bytes 0 & 1 of Address 0.
2 bytes of ROM that can be used to identify chips among others on the wafer. These bits
reduce the number of fuses necessary to construct a unique serial number. The ROM SN
is read by accessing ROM bytes 2 & 3 of Address 0. The serial number can always be
read by the system and is optionally included in the message digested by the MAC
command.
4 bytes of ROM that are used by Atmel to identify the design revision of the AT88SA100S
chip. These bytes can be freely read as the four bytes returned from ROM address 1,
however system code should not depend on this value as it may change from time to time.
fuse array, see below for more details.
These fuses can be written with the BurnFuse command and can always be read
with the Read command.
See Section 1.3. Set by Atmel, can’t be modified in the field
See Section 1.3. Set by Atmel, can’t be modified in the field
Each bit, when 0, locks the current value of the corresponding 16 bit block of the
Description
RETAIN
is still supplied to
8558B–SMEM–09/09