AT88RF04C-MY1G View Datasheet(PDF) - Atmel Corporation
Part Name
Description
Manufacturer
AT88RF04C-MY1G Datasheet PDF : 158 Pages
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AT88SC0808/1616/3216/6416CRF, AT88RF04C
Appendix G. Security Fuses
There are four fuses which control access to the Configuration Memory. One fuse (SEC) is programmed by Atmel
before CryptoRF leaves the factory; the remaining three fuses are programmed during the personalization process.
Once a fuse is programmed, it can never be changed.
These fuses do not control access to the user memory; user memory access rights are defined in the Access
Registers. The security fuses are used to lock the state of the Access Registers, Passwords, Keys, and other
configuration data during the personalization process so that they cannot be changed after a card is issued.
G.1.
Reading the Security Fuses
To read the fuses send the Read System Zone command with PARAM = $01, ADDR = $FF, L = $00. The CryptoRF
response will contain one data byte, the Fuse Byte. A value of 0b indicates the fuse has been programmed. Bits 4 to 7
of this byte are not used as security fuses and are reserved by Atmel.
Figure 20. Definition of the DATA Byte received when reading the Fuse Byte of 88SC PICCs.
F7
F6
F5
F4
F3
F2
F1
F0
RFU RFU RFU RFU SEC PER CMA FAB
X
X
X
X
0
1
1
1 Default Value
Figure 21. Definition of the DATA Byte received when reading the Fuse Byte of 88RF PICCs.
F7
F6
F5
F4
F3
F2
F1
F0
RFU RFU RFU RFU SEC ENC
SKY
PER
X
X
X
X
0
1
1
1
Default Value
G.2.
Programming the Fuse Bits
Three security fuses are programmed at the end of the personalization process to lock the PICC configuration. The
Write Fuse Byte option of the Write System Zone command is used to program the fuses. A fourth fuse, SEC, is
already programmed by Atmel before CryptoRF leaves the factory. The fuses can only be programmed in the specified
order.
The security fuse programming sequence is as follows:
1. Send Write System Zone command with:
PARAM = $01, ADDR = $06, L = $00, DATA = $00 to program the FAB or ENC fuse.
2. Send Write System Zone command with:
PARAM = $01, ADDR = $04, L = $00, DATA = $00 to program the CMA or SKY fuse.
3. Send Write System Zone command with:
PARAM = $01, ADDR = $00, L = $00, DATA = $00 to program the PER fuse.
The response to each Write System Zone command should be ACK, and the fuse byte contents will be returned in the
STATUS byte. After all three fuses are programmed, the device configuration is locked.
G.3.
Configuration Memory Access Control
Table 62 shows the Configuration Memory access conditions for each of the 88SC PICC security fuse settings. Table
63 shows the Configuration Memory access conditions for each of the 88RF PICC security fuse settings. The left
column contains the name of the register area in the Configuration Memory map. The next column indicates if that row
applies to Read System Zone commands or Write System Zone commands. The four columns to the right show the
security fuse states.
91
5276C–RFID–3/09
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