HT45F3W Datasheet, PDF (44/167 Pages) Holtek Semiconductor Inc – HT45F3W

HT45F3W
R-Type Blood Pressure Meter Flash MCU
Programming Considerations
Care must be taken that data is not inadvertently written to the EEPROM. Protection can be
enhanced 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 1 where
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 ; user defined address
MOV EEA, A
MOV A, 040H ; setup memory pointer MP1
MOV MP1, A ; MP1 points to EEC register
MOV A, 01H ; setup Bank Pointer
MOV BP, A
SET IAR1.1 ; set RDEN bit, enable read operations
SET IAR1.0 ; start Read Cycle - set RD bit
BACK:
SZ IAR1.0 ; check for read cycle end
JMP BACK
CLR IAR1 ; disable EEPROM read/write
CLR BP
MOV A, EED ; move read data to register
MOV READ_DATA, A
♦♦ Writing Data to the EEPROM – polling method
MOV A, EEPROM_ADRES ; user defined address
MOV EEA, A
MOV A, EEPROM_DATA ; user defined data
MOV EED, A
MOV A, 040H ; setup memory pointer MP1
MOV MP1, A ; MP1 points to EEC register
MOV A, 01H ; setup Bank Pointer
MOV BP, A
CLR EMI
SET IAR1.3 ; set WREN bit, enable write operations
SET IAR1.2 ; start Write Cycle - set WR bit
SET EMI
BACK:
SZ IAR1.2 ; check for write cycle end
JMP BACK
CLR IAR1 ; disable EEPROM read/write
CLR BP
Rev. 1.50
44
December 01, 2016