33.8.2 Serial Programming Algorithm

When writing serial data to the device, data is clocked on the rising edge of SCK.

When reading data from the device, data is clocked on the falling edge of SCK. Please refer to the figure, Serial Programming Waveforms in SPI Serial Programming Characteristics section for timing details.

To program and verify the device in the serial programming mode, the following sequence is recommended (See Serial Programming Instruction set in Table 33-18:

  1. Power-up sequence:


    Apply power between VCC and GND while RESET and SCK are set to “0”. In some systems, the programmer can not guarantee that SCK is held low during power-up. In this case, RESET must be given a positive pulse of at least two CPU clock cycles duration after SCK has been set to “0”.

  2. Wait for at least 20ms and enable serial programming by sending the Programming Enable serial instruction to pin MOSI.
  3. The serial programming instructions will not work if the communication is out of synchronization. When in sync. the second byte (0x53), will echo back when issuing the third byte of the Programming Enable instruction. Whether the echo is correct or not, all four bytes of the instruction must be transmitted. If the 0x53 did not echo back, give RESET a positive pulse and issue a new Programming Enable command.
  4. The Flash is programmed one page at a time. The memory page is loaded one byte at a time by supplying the 6 LSB of the address and data together with the Load Program Memory Page instruction. To ensure correct loading of the page, the data low byte must be loaded before data high byte is applied for a given address. The Program Memory Page is stored by loading the Write Program Memory Page instruction with the 7 MSB of the address. If polling (RDY/BSY) is not used, the user must wait at least tWD_FLASH before issuing the next page . Accessing the serial programming interface before the Flash write operation completes can result in incorrect programming.
  5. A: The EEPROM array is programmed one byte at a time by supplying the address and data together with the appropriate Write instruction. An EEPROM memory location is first automatically erased before new data is written. If polling (RDY/BSY) is not used, the user must wait at least tWD_EEPROM before issuing the next byte. In a chip erased device, no 0xFFs in the data file(s) need to be programmed.


    B: The EEPROM array is programmed one page at a time. The Memory page is loaded one byte at a time by supplying the 6 LSB of the address and data together with the Load EEPROM Memory Page instruction. The EEPROM Memory Page is stored by loading the Write EEPROM Memory Page Instruction with the 7 MSB of the address. When using EEPROM page access only byte locations loaded with the Load EEPROM Memory Page instruction is altered. The remaining locations remain unchanged. If polling (RDY/BSY) is not used, the used must wait at least tWD_EEPROM before issuing the next byte. In a chip erased device, no 0xFF in the data file(s) need to be programmed.

  6. Any memory location can be verified by using the Read instruction which returns the content at the selected address at serial output MISO.
  7. At the end of the programming session, RESET can be set high to commence normal operation.
  8. Power-off sequence (if needed):


    Set RESET to “1”.


    Turn VCC power off.

    Table 33-17. Typical Wait Delay Before Writing the Next Flash or EEPROM Location
    SymbolMinimum Wait Delay
    tWD_FLASH2.6ms
    tWD_EEPROM3.6ms
    tWD_ERASE10.5ms
    tWD_FUSE4.5ms