Datasheet
2001-2013 Microchip Technology Inc. DS39582C-page 39
PIC16F87XA
3.7 Protection Against Spurious Write
There are conditions when the device should not write
to the data EEPROM or Flash program memory. To
protect against spurious writes, various mechanisms
have been built-in. On power-up, WREN is cleared.
Also, the Power-up Timer (72 ms duration) prevents an
EEPROM write.
The write initiate sequence and the WREN bit together
help prevent an accidental write during brown-out,
power glitch or software malfunction.
3.8 Operation During Code-Protect
When the data EEPROM is code-protected, the micro-
controller can read and write to the EEPROM normally.
However, all external access to the EEPROM is
disabled. External write access to the program memory
is also disabled.
When program memory is code-protected, the microcon-
troller can read and write to program memory normally,
as well as execute instructions. Writes by the device may
be selectively inhibited to regions of the memory depend-
ing on the setting of bits WR1:WR0 of the configuration
word (see Section 14.1 “Configuration Bits” for addi-
tional information). External access to the memory is also
disabled.
TABLE 3-1: REGISTERS/BITS ASSOCIATED WITH DATA EEPROM AND
FLASH PROGRAM MEMORIES
Address Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Value on
Power-on
Reset
Value on
all other
Resets
10Ch EEDATA EEPROM/Flash Data Register Low Byte xxxx xxxx uuuu uuuu
10Dh EEADR EEPROM/Flash Address Register Low Byte xxxx xxxx uuuu uuuu
10Eh EEDATH
— — EEPROM/Flash Data Register High Byte xxxx xxxx ---0 q000
10Fh EEADRH
— — — EEPROM/Flash Address Register High Byte xxxx xxxx ---- ----
18Ch EECON1 EEPGD
— — — WRERR WREN WR RD x--- x000 ---0 q000
18Dh EECON2 EEPROM Control Register 2 (not a physical register) ---- ---- ---- ----
0Dh PIR2
— CMIF —EEIFBCLIF — — CCP2IF -0-0 0--0 -0-0 0--0
8Dh PIE2
— CMIE —EEIEBCLIE — — CCP2IE -0-0 0--0 -0-0 0--0
Legend: x = unknown, u = unchanged, - = unimplemented, read as ‘0’, q = value depends upon condition.
Shaded cells are not used by data EEPROM or Flash program memory.