PIC12F635/PIC16F636/639
The EEPROM data memory allows byte read and write.
A byte write automatically erases the location and
9.0
DATA EEPROM MEMORY
The EEPROM data memory is readable and writable
during normal operation (full VDD range). This memory
is not directly mapped in the register file space.
Instead, it is indirectly addressed through the Special
Function Registers. There are four SFRs used to read
and write this memory:
writes the new data (erase before write). The EEPROM
data memory is rated for high erase/write cycles. The
write time is controlled by an on-chip timer. The write
time will vary with voltage and temperature as well as
from chip-to-chip. Please refer to A/C specifications in
Section 15.0 “Electrical Specifications” for exact
limits.
• EECON1
• EECON2 (not a physically implemented register)
When the data memory is code-protected, the CPU
may continue to read and write the data EEPROM
memory. The device programmer can no longer access
the data EEPROM data and will read zeroes.
• EEDAT
• EEADR
EEDAT holds the 8-bit data for read/write and EEADR
holds the address of the EEPROM location being
accessed. PIC16F636/639 has 256 bytes of data
EEPROM and the PIC12F635 has 128 bytes.
REGISTER 9-1:
EEDAT: EEPROM DATA REGISTER
R/W-0
EEDAT7
bit 7
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
EEDAT6
EEDAT5
EEDAT4
EEDAT3
EEDAT2
EEDAT1
EEDAT0
bit 0
Legend:
R = Readable bit
-n = Value at POR
W = Writable bit
‘1’ = Bit is set
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared x = Bit is unknown
bit 7-0
EEDATn: Byte Value to Write To or Read From Data EEPROM bits
REGISTER 9-2:
EEADR: EEPROM ADDRESS REGISTER
R/W-0
EEADR7(1)
bit 7
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
EEADR6
EEADR5
EEADR4
EEADR3
EEADR2
EEADR1
EEADR0
bit 0
Legend:
R = Readable bit
-n = Value at POR
W = Writable bit
‘1’ = Bit is set
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared x = Bit is unknown
bit 7-0
EEADR: Specifies One of 256 Locations for EEPROM Read/Write Operation bits
Note 1: PIC16F636/639 only. Read as ‘0’ on PIC12F635.
© 2007 Microchip Technology Inc.
DS41232D-page 91
MICROCHIP [ MICROCHIP ]
