P�Og�A - Holtek HT66F488 Manual

Programming Considerations
Care must be taken that data is not inadvertently written to the EEPROM. Protection can be Periodic
by ensuring that the Write Enable bit is normally cleared to zero when not writing. Also the Bank
Pointer could be normally cleared to zero as this would inhibit access to Bank 1where the EEPROM
control register exist. Although certainly not necessary, consideration might be given in the
application program to the checking of the validity of new write data by a simple read back process.
When writing data the WR bit must be set high immediately after the WREN bit has been set high,
to ensure the write cycle executes correctly. The global interrupt bit EMI should also be cleared
before a write cycle is executed and then re-enabled after the write cycle starts. Note that the device
should not enter the IDLE or SLEEP mode until the EEPROM read or write operation is totally
complete. Otherwise, the EEPROM read or write operation will fail.
Programming Examples
Reading data from the EEPROM - polling method
MOV A, EEPROM_ADRES
MOV EEA, A
MOV A, 040H
MOV MP1L, A
MOV A, 01H
MOV MP1H, A
SET IAR1.1
SET IAR1.0
BACK:
SZ IAR1.0
JMP BACK
CLR IAR1
CLR BP
MOV A, EED
MOV READ_DATA, A
Writing Data to the EEPROM - polling method
MOV A, EEPROM_ADRES
MOV EEA, A
MOV A, EEPROM_DATA
MOV EED, A
MOV A, 040H
MOV MP1L, A
MOV A, 01H
MOV MP1H, A
CLR EMI
SET IAR1.3
SET IAR1.2
SET EMI
BACK:
SZ IAR1.2
JMP BACK
CLR IAR1
CLR MP1H
Rev. 1.21
A/D Flash MCU with EEPROM
; user defined address
; setup memory pointer MP1L
; MP1 points to EEC register
; setup memory pointer MP1H
; set RDEN bit, enable read operations
; start Read Cycle - set RD bit
; check for read cycle end
; disable EEPROM read/write
; move read data to register
; user defined address
; user defined data
; setup memory pointer MP1L
; MP1 points to EEC register
; setup memory pointer MP1H
; diable global interrupt
; set WREN bit, enable write operations
; start Write Cycle - set WR bit
; enable global interrupt
; check for write cycle end
; disable EEPROM write
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HT66F488/HT66F489
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