9.1.1 ROM Zone Registers
Each 256-bit memory zone has a corresponding single-bit ROM Zone register that is used to control the ROM status of that zone. These registers are nonvolatile and will retain their state even after a device power cycle or Reset operation. The following table outlines the two states of the ROM Zone registers. Each ROM Zone register has a specific ROM Zone register address that is reserved for read or write access.
| Value | ROM Zone Status |
|---|---|
0 | ROM Zone is not enabled and that memory zone can be programmed and erased (the default state). |
1 | ROM Zone is enabled and that memory zone can never be programmed or erased again. |
Issuing the ROM Zone command to a particular ROM Zone register address
will set the corresponding ROM Zone register to the logic ‘1’ state. Each
ROM Zone register can only be set once; therefore, once set to the logic
‘1’ state, a ROM Zone cannot be reset back to the logic
‘0’ state.
| Memory Zone | Starting Memory Address | Ending Memory Address | ROM Zone Register Address |
|---|---|---|---|
| 0 | 0h | 1Fh | 01h |
| 1 | 20h | 3Fh | 02h |
| 2 | 40h | 5Fh | 04h |
| 3 | 60h | 7Fh | 08h |