© 2004 Microchip Technology Inc. DS70052C-page 5-5
Section 5. Flash and EEPROM Programming
Flash and EEPROM
Programming
5
5.2.2.3 Write Byte Mode
To write a single program memory latch location in Byte mode, the following code sequence can
be used:
; Setup the address pointer to program space
MOV #tblpage(PROG_ADDR),W0 ; get table page value
MOV W0,TBLPAG ; load TBLPAG register
MOV #tbloffset(PROG_ADDR),W0 ; load address LS word
; Load data into working registers
MOV #LOW_BYTE,W2
MOV #MID_BYTE,W3
MOV #HIGH_BYTE,W4
; Write data to the latch
TBLWTH.B W4
,
[W0] ; write high byte
TBLWTL.B W2
,
[W0++] ; write low byte
TBLWTL.B W3
,
[W0++] ; write middle byte
In the code example above, the post-increment operator on the write to the low byte causes the
address in W0 to increment by one. This sets EA<0> = 1 for access to the middle byte in the third
write instruction. The last post-increment sets W0 back to an even address pointing to the next
program memory location.
5.3 Control Registers
Flash and data EEPROM programming operations are controlled using the following
Non-Volatile Memory (NVM) control registers:
• NVMCON: Non-Volatile Memory Control Register
• NVMKEY: Non-Volatile Memory Key Register
• NVMADR: Non-Volatile Memory Address Register
5.3.1 NVMCON Register
The NVMCON register is the primary control register for Flash and EEPROM program/erase
operations. This register selects Flash or EEPROM memory, whether an erase or program oper-
ation will be performed, and is used to start the program or erase cycle.
The NVMCON register is shown in Register 5-1. The lower byte of NVMCOM configures the type
of NVM operation that will be performed. For convenience, a summary of NVMCON setup values
for various program and erase operations is given in Table 5-1.
Table 5-1: NVMCON Register Values
NVMCON Register Values for RTSP Program and Erase Operations
Memory Type Operation Data Size NVMCON Value
Flash PM
Erase 1 row (32 instr. words) 0x4041
Program 1 row (32 instr. words) 0x4001
Data EEPROM
Erase
1 data word 0x4044
16 data words 0x4045
Program
1 data word 0x4004
16 data words 0x4005
Configuration Register
Write
(1)
1 config. register 0x4008
Note 1: The Device Configuration registers may be written to a new value without performing
an erase cycle.
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