参数资料
型号: T89C51CC01UA-SLSIM
厂商: Atmel
文件页数: 5/123页
文件大小: 0K
描述: IC 8051 MCU FLASH 32K 44PLCC
标准包装: 27
系列: AT89C CAN
核心处理器: 8051
芯体尺寸: 8-位
速度: 40MHz
连通性: CAN,UART/USART
外围设备: POR,PWM,WDT
输入/输出数: 32
程序存储器容量: 32KB(32K x 8)
程序存储器类型: 闪存
EEPROM 大小: 2K x 8
RAM 容量: 1.25K x 8
电压 - 电源 (Vcc/Vdd): 3 V ~ 5.5 V
数据转换器: A/D 8x10b
振荡器型: 外部
工作温度: -40°C ~ 85°C
封装/外壳: 44-LCC(J 形引线)
包装: 管件
配用: AT89STK-06-ND - KIT DEMOBOARD 8051 MCU W/CAN
其它名称: T89C51CC01UASLSIM
PIC18F2XK20/4XK20
DS41303G-page 102
2010 Microchip Technology Inc.
7.6
Operation During Code-Protect
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
information.
7.7
Protection Against Spurious Write
There are conditions when the user 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
the
Power-up
Timer
period
(TPWRT,
parameter 33).
The write initiate sequence and the WREN bit together
help prevent an accidental write during brown-out,
power glitch or software malfunction.
7.8
Using the Data EEPROM
The
data
EEPROM
is
a
high-endurance,
byte
addressable array that has been optimized for the
storage of frequently changing information (e.g.,
program variables or other data that are updated often).
When variables in one section change frequently, while
variables in another section do not change, it is possible
to exceed the total number of write cycles to the
EEPROM (specification D124) without exceeding the
total number of write cycles to a single byte (specification
D120). If this is the case, then 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:
DATA EEPROM REFRESH ROUTINE
Note:
If data EEPROM is only used to store
constants and/or data that changes rarely,
an array refresh is likely not required. See
specification.
CLRF
EEADR
; Start at address 0
BCF
EECON1, CFGS
; Set for memory
BCF
EECON1, EEPGD
; Set for Data EEPROM
BCF
INTCON, GIE
; Disable interrupts
BSF
EECON1, WREN
; Enable writes
Loop
; Loop to refresh array
BSF
EECON1, RD
; Read current address
MOVLW
55h
;
MOVWF
EECON2
; Write 55h
MOVLW
0AAh
;
MOVWF
EECON2
; Write 0AAh
BSF
EECON1, WR
; Set WR bit to begin write
BTFSC
EECON1, WR
; Wait for write to complete
BRA
$-2
INCFSZ
EEADR, F
; Increment address
BRA
LOOP
; Not zero, do it again
BCF
EECON1, WREN
; Disable writes
BSF
INTCON, GIE
; Enable interrupts
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