参数资料
型号: PIC18F248-E/SO
厂商: Microchip Technology
文件页数: 77/116页
文件大小: 0K
描述: IC MCU FLASH 8KX16 W/CAN 28-SOIC
产品培训模块: Asynchronous Stimulus
标准包装: 27
系列: PIC® 18F
核心处理器: PIC
芯体尺寸: 8-位
速度: 40MHz
连通性: CAN,I²C,SPI,UART/USART
外围设备: 欠压检测/复位,LVD,POR,PWM,WDT
输入/输出数: 22
程序存储器容量: 16KB(8K x 16)
程序存储器类型: 闪存
EEPROM 大小: 256 x 8
RAM 容量: 768 x 8
电压 - 电源 (Vcc/Vdd): 4.2 V ~ 5.5 V
数据转换器: A/D 5x10b
振荡器型: 外部
工作温度: -40°C ~ 125°C
封装/外壳: 28-SOIC(0.295",7.50mm 宽)
包装: 管件
2006 Microchip Technology Inc.
DS41159E-page 61
PIC18FXX8
5.3
Reading the Data EEPROM
Memory
To read a data memory location, the user must write the
address to the EEADR register, clear the EEPGD and
CFGS control bits (EECON1<7:6>) and then set
control bit RD (EECON1<0>). The data is available in
the very next instruction cycle of the EEDATA register;
therefore, it 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).
EXAMPLE 5-1:
DATA EEPROM READ
5.4
Writing to the Data EEPROM
Memory
To write an EEPROM data location, the address must
first be written to the EEADR register and the data writ-
ten to the EEDATA register. Then, the sequence in
Example 5-2 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 0AAh 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 exe-
cution (i.e., runaway programs). The WREN bit 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, clearing the
WREN bit will not affect the current write cycle. The WR
bit will be inhibited from being set unless the WREN bit
is set. The WREN bit must be set on a previous instruc-
tion. 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 roll this bit. EEIF must be
cleared by software.
EXAMPLE 5-2:
DATA EEPROM WRITE
MOVLW
DATA_EE_ADDR
;
MOVWF
EEADR
;Data Memory Address
;to read
BCF
EECON1, EEPGD
;Point to DATA memory
BCS
EECON1, CFGS
;
BSF
EECON1, RD
;EEPROM Read
MOVF
EEDATA, W
;W = EEDATA
MOVLW
DATA_EE_ADDR
;
MOVWF
EEADR
; Data Memory Address to read
MOVLW
DATA_EE_DATA
;
MOVWF
EEDATA
; Data Memory Value to write
BCF
EECON1, EEPGD
; Point to DATA memory
BCF
EECON1, CFGS
; Access program FLASH or Data EEPROM memory
BSF
EECON1, WREN
; Enable writes
BCF
INTCON, GIE
; Disable interrupts
Required
MOVLW
55h
;
Sequence
MOVWF
EECON2
; Write 55h
MOVLW
0AAh
;
MOVWF
EECON2
; Write AAh
BSF
EECON1, WR
; Set WR bit to begin write
BSF
INTCON, GIE
; Enable interrupts
.
; user code execution
.
BCF
EECON1, WREN
; Disable writes on write complete (EEIF set)
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