PIC24HJ128GP310 datasheet(56/286 Pages) MICROCHIP

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PIC24HJXXXGPX06/X08/X10

DS70175F-page 54

4.2

RTSP Operation

The PIC24HJXXXGPX06/X08/X10 Flash program

memory array is organized into rows of 64 instructions

or 192 bytes. RTSP allows the user 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. TABLE 23-12: “DC Characteristics: Program

Memory” displays typical erase and programming

times. 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 in sequential order. 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 set-

ting 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

There are two SFRs used to read and write the

program Flash memory: NVMCON and NVMKEY.

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 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. 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 oper-

ation is finished. Setting the WR bit (NVMCON<15>)

starts the operation, and the WR bit is automatically

cleared when the operation is finished.

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