31.1.9 FCW Sequencer User Model

Sequencer Enable Control

.KEY must be written with the WRKEY value before CTRLOP can be written to start a Write/Erase sequence. Once CTRLOP is written, the KEY register returns to 0’s (locks) and all registers in the FCW are write protected (BUSY = 1) until the operation finishes. Write protecting the registers prevents addresses, data and configuration changing mid sequence.

Start Sequencer

Once the NVM system is configured the only registers necessary for programming are CTRLOP, KEY, ADDR, and either DATAn or SRCADDR. Page Erase does not need DATAn or SRCADDR. And other Erases do not need ADDR.

For Write/Erase, the steps are as follows:

  1. Setup ADDR and if programming either DATAn (Single/Quad) or SRCADDR (Row Write).
  2. Write WRKEY to KEY.
  3. Write <Desired NVMOP> to CTRLOP.
  4. The FCW generates an interrupt when it clears STATUS.BUSY and sets INTFLAG.DONE.

When CTRLOP is written, the write/erase sequence starts and the CPU is unable to execute from the selected Flash panel for the duration of the sequence.