Datasheet

49
AT89C51AC3
4383D–8051–02/08
Figure 26. Flash and Extra Row Programming Procedure
Hardware Security Byte The following procedure is used to program the Hardware Security Byte space
and is summarized in Figure 27:
• Set FPS and map Hardware byte (FCON = 0x0C)
• Save and disable the interrupts.
• Load DPTR at address 0000h.
• Load Accumulator register with the data to load.
• Execute the MOVX @DPTR, A instruction.
• Launch the programming by writing the data sequence 54h followed by A4h in
FCON register (only from FM1).
The end of the programming indicated by the FBusy flag cleared.
• Restore the interrupts.
Flash Spaces
Programming
Save and Disable IT
EA = 0
Launch Programming
FCON = 5xh
FCON = Axh
End Programming
Restore IT
Column Latches Loading
see Figure 25
FBusy
Cleared?
Clear Mode
FCON = 00h