PIC24HJ12GP201 Datasheet, PDF (40/234 Pages) Microchip Technology – High-Performance, 16-Bit Microcontrollers

PIC24HJ12GP201/202
4.2 RTSP Operation
The PIC24HJ12GP201/202 Flash program memory
array is organized into rows of 64 instructions or 192
bytes. RTSP allows the user application to erase a
page of memory, which consists of eight rows (512
instructions) at a time, and to program one row or one
word at a time. The 8-row erase pages and single row
write rows are edge-aligned from the beginning of
program memory, on boundaries of 1536 bytes and
192 bytes, respectively.
The program memory implements holding buffers that
can contain 64 instructions of programming data. Prior
to the actual programming operation, the write data
must be loaded into the buffers sequentially. The
instruction words loaded must always be from a group
of 64 boundary.
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. A total
of 64 TBLWTL and TBLWTH instructions are required
to load the instructions.
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.
4.3 Control Registers
Two SFRs are used to read and write the program
Flash memory:
• NVMCON: Flash Memory Control Register
• NVMKEY: NonVolatile Memory Key Register
The NVMCON register (Register 4-1) controls which
blocks are to be erased, which memory type is to be
programmed and the start of the programming cycle.
NVMKEY (Register 4-2) is a write-only register that is
used for write protection. To start a programming or
erase sequence, the user application must
consecutively write 55h and AAh to the NVMKEY
register. Refer to Section 4.4 “Programming
Operations” for further details.
4.4 Programming Operations
A complete programming sequence is necessary for
programming or erasing the internal Flash in RTSP
mode. A programming operation is nominally 4 ms in
duration and the processor stalls (waits) until the
operation is finished. Setting the WR bit
(NVMCON<15>) starts the operation, and the WR bit is
automatically cleared when the operation is finished.
DS70282B-page 38
Preliminary
© 2007 Microchip Technology Inc.