AT89C51RD2-RDTIM Atmel, AT89C51RD2-RDTIM Datasheet - Page 89

• Manufacturer Part Number: AT89C51RD2-RDTIM
• Description: MCU 8-Bit AT89 80C51 CISC 64KB Flash 3.3V/5V 64-Pin VQFP Tray
• Manufacturer: Atmel

23. EEPROM Data Memory
23.1
4235J–8051–01/08
Write Data
This feature is available only for the AT89C51ED2 device.
The 2K bytes on-chip EEPROM memory block is located at addresses 0000h to 07FFh of the
XRAM/ERAM memory space and is selected by setting control bits in the EECON register.
A read or write access to the EEPROM memory is done with a MOVX instruction.
Data is written by byte to the EEPROM memory block as for an external RAM memory.
The following procedure is used to write to the EEPROM memory:
Figure 23-1 represents the optimal write sequence to the on-chip EEPROM data memory.
• Check EEBUSY flag
• If the user application interrupts routines use XRAM memory space: Save and disable
• Load DPTR with the address to write
• Store A register with the data to be written
• Set bit EEE of EECON register
• Execute a MOVX @DPTR, A
• Clear bit EEE of EECON register
• Restore interrupts.
• EEBUSY flag in EECON is then set by hardware to indicate that programming is in progress
• The end of programming is indicated by a hardware clear of the EEBUSY flag.
interrupts.
and that the EEPROM segment is not available for reading or writing.
AT89C51RD2/ED2
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