12 NVM - Nonvolatile Memory Control

Nonvolatile Memory (NVM) is separated into two types: Program Flash Memory (PFM) and Data EEPROM Memory.

PFM, Data EEPROM, User IDs and Configuration bits can all be selected for write access with the NVMREG bits. The NVMREG bits are don't cares for read access.

The write time is controlled by an on-chip timer. The write/erase voltages are generated by an on-chip charge pump rated to operate over the operating voltage range of the device.

NVM can be protected in two ways, by either code protection or write protection. Code protection (CP and CPD bits in the Configuration Words) disables access, reading and writing to both PFM and Data EEPROM Memory via external device programmers. Code protection does not affect the self-write and erase functionality. Code protection can only be reset by a device programmer performing a Bulk Erase to the device, clearing all nonvolatile memory, Configuration bits and User IDs.

Write protection prohibits self-write and erase to a portion or all of the PFM, as defined by the WRT bits in the Configuration Words. Write protection does not affect a device programmer’s ability to read, write or erase the device.

Table 12-1. NVM Organization and Access Information
Memory	PC[20:0] ICSP™ Addr[21:0] TBLPTR[21:0]	Execution	User Access
Memory	PC[20:0] ICSP™ Addr[21:0] TBLPTR[21:0]	CPU Execution	NVMREG	TABLAT	NVMDAT
User Flash Memory (PFM)	00 0000h  • • • 01 FFFFh	Read	10	Read/ Write⁽¹⁾	—⁽³⁾
User IDs⁽²⁾	20 0000h • • • 20 000Fh	No Access	x1	Read/ Write	—⁽³⁾
Reserved	20 0010h	No Access	—⁽³⁾
Reserved	2F FFFFh	No Access	—⁽³⁾
Configuration	30 0000h • • • 30 0000Bh	No Access	x1	Read/ Write⁽¹⁾	—⁽³⁾
Reserved	30 000Ch	No Access	—⁽³⁾
Reserved	30 FFFFh	No Access	—⁽³⁾
User Data Memory (Data EEPROM)	31 0000h • • • 31 0YYYh⁽⁴⁾	No Access	00	—⁽³⁾	Read/ Write⁽¹⁾
Reserved	32 0000h	No Access	—⁽³⁾
Reserved	3F FFFBh	No Access	—⁽³⁾
Revision ID/ Device ID	3F FFFCh • • • 3F FFFFh	No Access	x1	Read	—⁽³⁾
Note: Subject to Memory Write Protection settings. User IDs are eight words. There is no code protection, table read protection or write protection implemented for this region. Reads as ‘`0`’. Writes set the WRERR bit and clear the WR bit. Address range shown is for ICSP only. User mode read and write must use NVMADR with upper limit of 0YYYh to specify the address. YYY is the hexadecimal equivalent of one less than the number of bytes in the EEPROM data memory.