Datasheet

© 2007 Microchip Technology Inc. DS39907A-page 33
PIC24FJXXXGA1/GB1
4.6.4 CODE-PROTECT CONFIGURATION
BITS
PIC24FJXXXGA1/GB1 family devices provide two
complimentary methods to protect application code
from overwrites and erasures. These also help to pro-
tect the device from inadvertent configuration changes
during run time. Additional information is available in
the product data sheet.
4.6.4.1 GENERAL SEGMENT
PROTECTION
For all devices in the PIC24FJXXXGA1/GB1 families,
the on-chip program memory space is treated as a
single block, known as the General Segment (GS).
Code protection for this block is controlled by one Con-
figuration bit, GCP. This bit inhibits external reads and
writes to the program memory space. It has no direct
effect in normal execution mode.
Write protection is controlled by the GWRP bit in the
Configuration Word. When GWRP is programmed to
‘0’, internal write and erase operations to program
memory are blocked.
4.6.4.2 CODE SEGMENT PROTECTION
In addition to global General Segment protection, a
separate subrange of the program memory space can
be individually protected against writes and erases.
This area can be used for many purposes where a
separate block of write and erase-protected code is
needed, such as bootloader applications. Unlike
common boot block implementations, the specially pro-
tected segment in PIC24FJXXXGA1/GB1 devices can
be located by the user anywhere in the program space,
and configured in a wide range of sizes.
Code segment protection provides an added level of
protection to a designated area of program memory by
disabling the NVM safety interlock whenever a write or
erase address falls within a specified range. It does not
override general segment protection controlled by the
GCP or GWRP bits. For example, if GCP and GWRP
are enabled, enabling segmented code protection for
the bottom half of program memory does not undo
general segment protection for the top half.
4.7 Exiting Enhanced ICSP Mode
Exiting Program/Verify mode is done by removing VIH
from MCLR, as shown in Figure 4-6. The only require-
ment for exit is that an interval, P16, should elapse
between the last clock and program signals on PGCx
and PGDx before removing V
IH.
FIGURE 4-6: EXITING ENHANCED
ICSP™ MODE
Note: Bulk Erasing in ICSP mode is the only way
to reprogram code-protect bits from an ON
state (‘0’) to an Off state (‘1’).
MCLR
P16
PGDx
PGDx = Input
PGCx
VDD
VIH
VIH
P17