PIC16F630/676
of the read or write operation. The inability to clear the
WR bit in software prevents the accidental, premature
termination of a write operation.
8.1
EEADR
The EEADR register can address up to a maximum of
128 bytes of data EEPROM. Only seven of the eight
bits in the register (EEADR<6:0>) are required. The
MSb (bit 7) is ignored.
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 EEDATA and EEADR registers will
need to be re-initialized.
The upper bit should always be ‘0’ to remain upward
compatible with devices that have more data EEPROM
memory.
8.2
EECON1 AND EECON2
REGISTERS
Interrupt flag bit EEIF in the PIR1 register is set when
write is complete. This bit must be cleared in software.
EECON1 is the control register with four low order bits
physically implemented. The upper four bits are non-
implemented and read as '0's.
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.
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
REGISTER 8-3:
EECON1 — EEPROM CONTROL REGISTER (ADDRESS: 9Ch)
U-0
—
U-0
—
U-0
—
U-0
—
R/W-x
R/W-0
WREN
R/S-0
WR
R/S-0
RD
WRERR
bit 7
bit 0
bit 7-4
bit 3
Unimplemented: Read as ‘0’
WRERR: EEPROM Error Flag bit
1=A write operation is prematurely terminated (any MCLR Reset, any WDT Reset during
normal operation or BOD detect)
0=The write operation completed
bit 2
bit 1
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
can only be set, not cleared, in software.)
0= Write cycle to the data EEPROM is complete
bit 0
RD: Read Control bit
1= Initiates an EEPROM read (Read takes one cycle. RD is cleared in hardware. The RD bit
can only be set, not cleared, in software.)
0= Does not initiate an EEPROM read
Legend:
S = Bit can only be set
R = Readable bit
W = Writable bit
’1’ = Bit is set
U = Unimplemented bit, read as ‘0’
’0’ = Bit is cleared x = Bit is unknown
- n = Value at POR
DS40039E-page 50
© 2007 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
