16F84A Microchip Technology, 16F84A Datasheet - Page 19

• Manufacturer Part Number: 16F84A
• Description: 18-pin Enhanced Flash/EEPROM 8-Bit Microcontroller
• Manufacturer: Microchip Technology

5.0
The EEPROM data memory is readable and writable
during normal operation (full V
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. These registers are:
• EECON1
• EECON2 (Not a physically implemented register)
• EEDATA
• EEADR
EEDATA holds the 8-bit data for read/write, and EEADR
holds the address of the EEPROM location being
accessed. PIC16F84A devices have 64 bytes of data
EEPROM with an address range from 0h to 3Fh.
FIGURE 5-1:
1998 Microchip Technology Inc.
bit 7:5
bit 4
bit 3
bit 2
bit 1
bit 0
bit7
—
U
DATA EEPROM MEMORY
Unimplemented: Read as '0'
EEIF: EEPROM Write Operation Interrupt Flag bit
1 = The write operation completed (must be cleared in software)
0 = The write operation is not complete or has not been started
WRERR: EEPROM Error Flag bit
1 = A write operation is prematurely terminated
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 can only
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 can only
0 = Does not initiate an EEPROM read
—
U
(any MCLR reset or any WDT reset during normal operation)
be set (not cleared) in software.
be set (not cleared) in software).
EECON1 REGISTER (ADDRESS 88h)
—
U
DD
R/W-0
range). This memory
EEIF
WRERR
R/W-x
Preliminary
WREN
R/W-0
The EEPROM data memory allows byte read and write.
A byte write automatically erases the location and
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 AC specifications for
exact limits.
When the device is code protected, the CPU may
continue to read and write the data EEPROM memory.
The device programmer can no longer access
this memory.
Additional information on the Data EEPROM is avail-
able in the PICmicro™ Mid-Range Reference Manual,
(DS33023).
R/S-0
WR
R/S-x
RD
bit0
R = Readable bit
W = Writable bit
S = Settable bit
U = Unimplemented bit,
- n = Value at POR reset
PIC16F84A
read as ‘0’
DS35007A-page 19