Datasheet

dsPIC33FJXXXGPX06A/X08A/X10A
DS70593D-page 78  2009-2012 Microchip Technology Inc.
5.2 RTSP Operation
The dsPIC33FJXXXGPX06A/X08A/X10A Flash pro-
gram 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 25-12 illustrates typical erase
and programming times. The 8-row erase pages and
single row write rows are edge-aligned, from the begin-
ning 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
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.
5.3 Programming Operations
A complete programming sequence is necessary for
programming or erasing the internal Flash in RTSP
mode. The processor stalls (waits) until the
programming operation is finished.
The programming time depends on the FRC accuracy
(see Table 25-19) and the value of the FRC Oscillator
Tuning register (see Register 9-4). Use the following
formula to calculate the minimum and maximum values
for the Row Write Time, Page Erase Time and Word
Write Cycle Time parameters (see Table 25-12).
EQUATION 5-1: PROGRAMMING TIME
For example, if the device is operating at +125°C, the
FRC accuracy will be ±5%. If the TUN<5:0> bits (see
Register 9-4) are set to ‘b111111, the minimum row
write time is equal to Equation 5-2.
EQUATION 5-2: MINIMUM ROW WRITE
TIME
The maximum row write time is equal to Equation 5-3.
EQUATION 5-3: MAXIMUM ROW WRITE
TIME
Setting the WR bit (NVMCON<15>) starts the
operation, and the WR bit is automatically cleared
when the operation is finished.
5.4 Control Registers
The two SFRs that are used to read and write the
program Flash memory are:
• NVMCON: Flash Memory Control Register
• NVMKEY: Non-Volatile Memory Key Register
The NVMCON register (Register 5-1) controls which
blocks are to be erased, which memory type is to be
programmed and the start of the programming cycle.
NVMKEY (Register 5-2) is a write-only register that is
used for write protection. To start a programming or
erase sequence, the user must consecutively write 0x55
and 0xAA to the NVMKEY register. Refer to Section 5.3
“Programming Operations” for further details.
T
7.37 MHz FRC Accuracy% FRC Tuning%
--------------------------------------------------------------------------------------------------------------------------
T
RW
11064 Cycles
7.37 MHz 10.05+1 0.00375–
---------------------------------------------------------------------------------------------- 1 . 4 3 5 ms==
T
RW
11064 Cycles
7.37 MHz 10.05–1 0.00375–
----------------------------------------------------------------------------------------------1.586ms==