3.1.3.7 Program Access Enable
The Program Access Enable command
is used to enable the access to the SAFLOCK and
ICSPDIS bits. By default, write access to the
SAFLOCK and ICSPDIS bits is
blocked for safety to prevent inadvertent and irreversible changes to device
configuration. Refer to Enhanced Code Protection for details. Using the Program Data command to write to these CONFIG bits will not
work without sending the Program Access Enable command first. Sending the Program Access
Enable (0x4C
) command with the 22'h27A1A5
payload (the
total 32-bit value is 32'h4C4F434B
, more easily remembered as LOCK in
ASCII) will grant write access to these Configuration bits for a limited-time command
window. The write access is terminated once the command window has passed, regardless of
the command that is executed during that window. On PIC18 devices, the write-access
window is for a duration of one command, so the Program Access Enable command must be
issued immediately before every write to the SAFLOCK or
ICSPDIS bits.