PIC12F639 Microchip Technology, PIC12F639 Datasheet - Page 76

• Manufacturer Part Number: PIC12F639
• Description: (PIC12F635 / PIC12F636 / PIC12F639) 8/14-PIN FLASH-BASED / 8-BIT CMOS MICROCONTROLLERS WITH NANOWATT TECHNOLOGY
• Manufacturer: Microchip Technology

PIC12F635/PIC16F636/639
9.1
EECON1 is the control register with four low-order bits
physically implemented. The upper four bits are non-
implemented and read as ‘0’s.
Control bits RD and WR initiate read and write,
respectively. These bits cannot be cleared, only set in
software. They are cleared in hardware at completion
of the read or write operation. The inability to clear the
WR bit in software prevents the accidental, premature
termination of a write operation.
REGISTER 9-3:
DS41232B-page 74
EECON1 AND EECON2 Registers
bit 7-4
bit 3
bit 2
bit 1
bit 0
EECON1 – EEPROM CONTROL 1 REGISTER (ADDRESS: 9Ch)
bit 7
Unimplemented: Read as ‘0’
WRERR: EEPROM Error Flag bit
1 = A write operation is prematurely terminated (any MCLR Reset, any WDT Reset during
0 = The write operation completed
WREN: EEPROM Write Enable bit
1 = Allows write cycles
0 = Inhibits write to the data EEPROM
WR: Write Control bit
1 = Initiates a write cycle (The bit is cleared by hardware once write is complete. The WR bit
0 = Write cycle to the data EEPROM is complete
RD: Read Control bit
1 = Initiates an EEPROM read (Read takes one cycle. RD is cleared in hardware. The RD bit
0 = Does not initiate an EEPROM read
Legend:
S = Bit can only be set
R = Readable bit
- n = Value at POR
U-0
—
normal operation or BOD detect)
can only be set, not cleared, in software.)
can only be set, not cleared, in software.)
U-0
—
U-0
Preliminary
—
W = Writable bit
‘1’ = Bit is set
U-0
—
The WREN bit, when set, will allow a write operation.
On power-up, the WREN bit is clear. The WRERR bit is
set when a write operation is interrupted by a MCLR
Reset, or a WDT Time-out Reset during normal
operation. In these situations, following Reset, the user
can check the WRERR bit, clear it and rewrite the
location. The data and address will be cleared.
Therefore, the EEDAT and EEADR registers will need
to be re-initialized.
Interrupt flag, EEIF bit (PIR1<7>), is set when write is
complete. This bit must be cleared in software.
EECON2 is not a physical register. Reading EECON2
will read all ‘0’s. The EECON2 register is used
exclusively in the data EEPROM write sequence.
Note:
WRERR
R/W-x
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
The EECON1, EEDAT and EEADR
registers should not be modified during a
data EEPROM write (WR bit = 1).
WREN
R/W-0
© 2005 Microchip Technology Inc.
x = Bit is unknown
R/S-0
WR
R/S-0
RD
bit 0