SAM7X256_14 Datasheet, PDF (106/662 Pages) ATMEL Corporation – ARM-based Flash MCU

 If the general-purpose bit number is greater than the total number of general-purpose bits, then the command has
no effect.
It is possible to deactivate a general-purpose NVM bit set previously. The clear sequence is:
 Start the Clear General-purpose Bit command (CGPB) by writing the Flash Command Register with CGPB and the
number of the general-purpose bit to be cleared in the PAGEN field.
 When the clear completes, the bit FRDY in the Flash Programming Status Register (MC_FSR) rises. If an interrupt
has been enabled by setting the bit FRDY in MC_FMR, the interrupt line of the Memory Controller is activated.
Two errors can be detected in the MC_FSR register after a programming sequence:
 Programming Error: a bad keyword and/or an invalid command have been written in the MC_FCR register
 If the number of the general-purpose bit set in the PAGEN field is greater than the total number of general-purpose
bits, then the command has no effect.
The Clear General-purpose Bit command programs the general-purpose NVM bit to 0; the corresponding bit GPNVM0 to
GPNVMx in MC_FSR reads 0. The Set General-purpose Bit command programs the general-purpose NVM bit to 1; the
corresponding bit GPNVMx in MC_FSR reads 1.
Note: Access to the Flash in read mode is permitted when a Set, Clear or Get General-purpose NVM Bit command is
performed.
19.2.4.5 Security Bit
The goal of the security bit is to prevent external access to the internal bus system. (Does not apply to EFC1 on the
AT91SAM7X512.) JTAG, Fast Flash Programming and Flash Serial Test Interface features are disabled. Once set, this
bit can be reset only by an external hardware ERASE request to the chip. Refer to the product definition section for the
pin name that controls the ERASE. In this case, the full memory plane is erased and all lock and general-purpose NVM
bits are cleared. The security bit in the MC_FSR is cleared only after these operations. The activation sequence is:
 Start the Set Security Bit command (SSB) by writing the Flash Command Register.
 When the locking completes, the bit FRDY in the Flash Programming Status Register (MC_FSR) rises. If an
interrupt has been enabled by setting the bit FRDY in MC_FMR, the interrupt line of the Memory Controller is
activated.
When the security bit is active, the SECURITY bit in the MC_FSR is set.
SAM7X Series [DATASHEET]
6120K–ATARM–11-Feb-14
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