PIC24FJ64GA004-IPT Datasheet, PDF (32/52 Pages) Microchip Technology – PIC24FJXXXGA0XX Flash Programming Specification

PIC24FJXXXGA0XX
4.6.2 PROGRAMMING METHODOLOGY
Configuration bits may be programmed a single byte at
a time using the PROGW command. This command
specifies the configuration data and Configuration
register address. When Configuration bits are
programmed, any unimplemented or reserved bits
must be programmed with a ‘1’.
Two PROGW commands are required to program the
Configuration bits. A flowchart for Configuration bit
programming is shown in Figure 4-5.
Note:
If the General Segment Code-Protect bit
(GCP) is programmed to ‘0’, code memory
is code-protected and can not be read.
Code memory must be verified before
enabling read protection. See Section 4.6.4
“Code-Protect Configuration Bits” for
more information about code-protect
Configuration bits.
4.6.3 PROGRAMMING VERIFICATION
After the Configuration bits are programmed, the
contents of memory should be verified to ensure that
the programming was successful. Verification requires
the Configuration bits to be read back and compared
against the copy held in the programmer’s buffer. The
READP command reads back the programmed
Configuration bits and verifies that the programming
was successful.
4.6.4
CODE-PROTECT
CONFIGURATION BITS
CW1 Configuration register controls code protection for
the PIC24FJXXXGA0XX family. Two forms of code pro-
tection are provided. One form prevents code memory
from being written (write protection) and the other
prevents code memory from being read (read protection).
GWRP (CW1<12>) controls write protection and GCP
(CW1<13>) controls read protection. Protection is
enabled when the respective bit is ‘0’.
Erasing sets GWRP and GCP to ‘1’, which allows the
device to be programmed.
When write protection is enabled (GWRP = 0), any
programming operation to code memory will fail.
When read protection is enabled (GCP = 0), any read
from code memory will cause a 0h to be read, regard-
less of the actual contents of code memory. Since the
programming executive always verifies what it
programs, attempting to program code memory with
read protection enabled also will result in failure.
It is imperative that both GWRP and GCP are ‘1’ while
the device is being programmed and verified. Only after
the device is programmed and verified should either
GWRP or GCP be programmed to ‘0’ (see Section 4.6
“Configuration Bits Programming”).
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’).
DS39768D-page 32
© 2008 Microchip Technology Inc.