SAM7S256_14 Datasheet, PDF (141/775 Pages) ATMEL Corporation – ARM-based Flash MCU

20.3.4.6 Flash Security Bit Command
Security bits can be set using Set Security Bit command (SSE). Once the security bit is active, the Fast Flash pro-
gramming is disabled. No other command can be run. Only an event on the Erase pin can erase the security bit
once the contents of the Flash have been erased.
The SAM7S512 security bit is controlled by the EFC0. To use the Set Security Bit command, the EFC0 must be
selected using the Select EFC command.
Table 20-29. Set Security Bit Command
Read/Write
DR Data
Write
SSE
Once the security bit is set, it is not possible to access FFPI. The only way to erase the security bit is to erase the
Flash.
In order to erase the Flash, the user must perform the following:
• Power-off the chip
• Power-on the chip with TST = 0
• Assert Erase during a period of more than 220 ms
• Power-off the chip
Then it is possible to return to FFPI mode and check that Flash is erased.
20.3.4.7 SAM7S512 Select EFC Command
The commands WPx, EA, xLB, xFB are executed using the current EFC controller. The default EFC controller is
EFC0. The Select EFC command (SEFC) allows selection of the current EFC controller.
Table 20-30. Select EFC Command
Step Handshake Sequence
1
Write handshaking
2
Write handshaking
MODE[3:0]
CMDE
DATA
DATA[15:0]
SEFC
0 = Select EFC0
1 = Select EFC1
SAM7S Series [DATASHEET]
6175M–ATARM–26-Oct-12
141