PIC18F4620-I/P Microchip Technology Inc., PIC18F4620-I/P Datasheet - Page 88

• Manufacturer Part Number: PIC18F4620-I/P
• Description: 40 Pin, 64 KB Flash, 3968 RAM, 36 I/O
• Manufacturer: Microchip Technology Inc.

Specifications of PIC18F4620-I/P

• A/d Inputs: 13-Channel, 10-Bit
• Comparators: 2
• Cpu Speed: 10 MIPS
• Eeprom Memory: 1024 Bytes
• Input Output: 36
• Interface: SPI/I2C/USART
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 40-pin PDIP
• Programmable Memory: 64K Bytes
• Ram Size: 4K Bytes
• Speed: 40 MHz
• Timers: 1-8 bit, 3-16 bit
• Voltage, Range: 2-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

PIC18F2525/2620/4525/4620
7.6
Data EEPROM memory has its own code-protect bits in
configuration words. External read and write operations
are disabled if code protection is enabled.
The microcontroller itself can both read and write to the
internal data EEPROM, regardless of the state of the
code-protect configuration bit. Refer to Section 23.0
“Special Features of the CPU” for additional
information.
7.7
There are conditions when the device may not want to
write to the data EEPROM memory. To protect against
spurious EEPROM writes, various mechanisms have
been implemented. On power-up, the WREN bit is
cleared. In addition, writes to the EEPROM are blocked
during
parameter 33).
The write initiate sequence and the WREN bit together
help prevent an accidental write during Brown-out
Reset, power glitch or software malfunction.
EXAMPLE 7-3:
DS39626B-page 86
Loop
Operation During Code-Protect
Protection Against Spurious Write
the
CLRF
CLRF
BCF
BCF
BCF
BSF
BSF
MOVLW
MOVWF
MOVLW
MOVWF
BSF
BTFSC
BRA
INCFSZ
BRA
INCFSZ
BRA
BCF
BSF
Power-up
EEADR
EEADRH
EECON1, CFGS
EECON1, EEPGD
INTCON, GIE
EECON1, WREN
EECON1, RD
55h
EECON2
0AAh
EECON2
EECON1, WR
EECON1, WR
$-2
EEADR, F
LOOP
EEADRH, F
LOOP
EECON1, WREN
INTCON, GIE
DATA EEPROM REFRESH ROUTINE
Timer
period
; Start at address 0
;
; Set for memory
; Set for Data EEPROM
; Disable interrupts
; Enable writes
; Loop to refresh array
; Read current address
;
; Write 55h
;
; Write 0AAh
; Set WR bit to begin write
; Wait for write to complete
; Increment address
; Not zero, do it again
; Increment the high address
; Not zero, do it again
; Disable writes
; Enable interrupts
(T
PWRT
Preliminary
,
7.8
The data EEPROM is a high endurance, byte address-
able array that has been optimized for the storage of
frequently
variables or other data that are updated often).
Frequently changing values will typically be updated
more often than specification D124. If this is not the
case, an array refresh must be performed. For this
reason, variables that change infrequently (such as
constants, IDs, calibration, etc.) should be stored in
Flash program memory.
A simple data EEPROM refresh routine is shown in
Example 7-3.
Note:
Using the Data EEPROM
If data EEPROM is only used to store
constants and/or data that changes often,
an array refresh is likely not required. See
specification D124.
changing
 2004 Microchip Technology Inc.
information
(e.g.,
program