PIC18F8520-I/PT Microchip Technology Inc., PIC18F8520-I/PT Datasheet - Page 83

• Manufacturer Part Number: PIC18F8520-I/PT
• Description: 80 PIN, 32 KB FLASH, 2048 RAM, 68 I/O
• Manufacturer: Microchip Technology Inc.

Specifications of PIC18F8520-I/PT

• A/d Inputs: 16-Channel, 10-Bit
• Comparators: 2
• Cpu Speed: 10 MIPS
• Eeprom Memory: 1024 Bytes
• Input Output: 68
• Interface: I2C/SPI/UART/USART
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 80-pin TQFP
• Programmable Memory: 32K Bytes
• Ram Size: 2K Bytes
• Speed: 40 MHz
• Timers: 2-8-bit, 3-16-bit
• Voltage, Range: 2-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part

7.3
To read a data memory location, the user must write the
address to the EEADRH:EEADR register pair, clear the
EEPGD control bit (EECON1<7>), clear the CFGS
EXAMPLE 7-1:
7.4
To write an EEPROM data location, the address must
first be written to the EEADRH:EEADR register pair
and the data written to the EEDATA register. Then the
sequence in Example 7-2 must be followed to initiate
the write cycle.
The write will not initiate if the above sequence is not
exactly followed (write 55h to EECON2, write AAh to
EECON2, then set WR bit) for each byte. It is strongly
recommended that interrupts be disabled during this
code segment.
Additionally, the WREN bit in EECON1 must be set to
enable writes. This mechanism prevents accidental
writes to data EEPROM due to unexpected code
execution (i.e., runaway programs). The WREN bit
EXAMPLE 7-2:
 2004 Microchip Technology Inc.
MOVLW
MOVWF
MOVLW
MOVWF
BCF
BCF
BSF
MOVF
Required
Sequence
Reading the Data EEPROM
Memory
Writing to the Data EEPROM
Memory
DATA_EE_ADDRH
EEADRH
DATA_EE_ADDR
EEADR
EECON1, EEPGD
EECON1, CFGS
EECON1, RD
EEDATA, W
PIC18F6520/8520/6620/8620/6720/8720
MOVLW
MOVWF
MOVLW
MOVWF
MOVLW
MOVWF
BCF
BCF
BSF
BCF
MOVLW
MOVWF
MOVLW
MOVWF
BSF
BSF
BCF
DATA EEPROM READ
DATA EEPROM WRITE
DATA_EE_ADDRH
EEADRH
DATA_EE_ADDR
EEADR
DATA_EE_DATA
EEDATA
EECON1, EEPGD
EECON1, CFGS
EECON1, WREN
INTCON, GIE
55h
EECON2
AAh
EECON2
EECON1, WR
INTCON, GIE
EECON1, WREN
;
; Upper bits of Data Memory Address to read
;
; Lower bits of Data Memory Address to read
; Point to DATA memory
; Access EEPROM
; EEPROM Read
; W = EEDATA
;
; Upper bits of Data Memory Address to write
;
; Lower bits of Data Memory Address to write
;
; Data Memory Value to write
; Point to DATA memory
; Access EEPROM
; Enable writes
; Disable Interrupts
;
; Write 55h
;
; Write AAh
; Set WR bit to begin write
; Enable Interrupts
; User code execution
; Disable writes on write complete (EEIF set)
control bit (EECON1<6>) and then set the RD control
bit (EECON1<0>). The data is available for the very
next instruction cycle; therefore, the EEDATA register
can be read by the next instruction. EEDATA will hold
this value until another read operation, or until it is
written to by the user (during a write operation).
should be kept clear at all times, except when updating
the EEPROM. The WREN bit is not cleared
by hardware
After a write sequence has been initiated, EECON1,
EEADRH, EEADR and EEDATA cannot be modified.
The WR bit will be inhibited from being set unless the
WREN bit is set. Both WR and WREN cannot be set
with the same instruction.
At the completion of the write cycle, the WR bit is
cleared in hardware and the EEPROM Write Complete
Interrupt Flag bit (EEIF) is set. The user may either
enable this interrupt, or poll this bit. EEIF must be
cleared by software.
DS39609B-page 81