Datasheet

PIC24FV32KA304 FAMILY
DS30009995E-page 58  2011-2017 Microchip Technology Inc.
5.2 RTSP Operation
The PIC24F Flash program memory array is organized
into rows of 32 instructions or 96 bytes. RTSP allows
the user to erase blocks of 1 row, 2 rows and 4 rows
(32, 64 and 128 instructions) at a time, and to program
one row at a time. It is also possible to program single
words.
The 1-row (96 bytes), 2-row (192 bytes) and 4-row
(384 bytes) erase blocks, and single row write block
(96 bytes) are edge-aligned from the beginning of
program memory.
When data is written to program memory using TBLWT
instructions, the data is not written directly to memory.
Instead, data written using Table Writes is stored in holding
latches until the programming sequence is executed.
Any number of TBLWT instructions can be executed
and a write will be successfully performed. However,
32 TBLWT instructions are required to write the full row
of memory.
The basic sequence for RTSP programming is to set up
a Table Pointer, then do a series of TBLWT instructions to
load the buffers. Programming is performed by setting
the control bits in the NVMCON register.
Data can be loaded in any order and the holding registers
can be written to multiple times before performing a write
operation. Subsequent writes, however, will wipe out any
previous writes.
All of the Table Write operations are single-word writes
(two instruction cycles), because only the buffers
are written. A programming cycle is required for
programming each row.
5.3 Enhanced In-Circuit Serial
Programming
Enhanced ICSP uses an on-board bootloader, known as
the Programming Executive (PE), to manage the pro-
gramming process. Using an SPI data frame format, the
Programming Executive can erase, program and verify
program memory. For more information on Enhanced
ICSP, see the device programming specification.
5.4 Control Registers
There are two SFRs used to read and write the
program Flash memory: NVMCON and NVMKEY.
The NVMCON register (Register 5-1) controls the blocks
that need to be erased, which memory type is to be
programmed and when the programming cycle starts.
NVMKEY is a write-only register that is used for write
protection. To start a programming or erase sequence,
the user must consecutively write 55h and AAh to the
NVMKEY register. For more information, refer to
Section 5.5 “Programming Operations”.
5.5 Programming Operations
A complete programming sequence is necessary for
programming or erasing the internal Flash in RTSP
mode. During a program or erase operation, the
processor stalls (Waits) until the operation is finished.
Setting the WR bit (NVMCON<15>) starts the opera-
tion and the WR bit is automatically cleared when the
operation is finished.
Note: Writing to a location multiple times without
erasing it is not recommended.