PIC32MX440F256H-80I Datasheet, PDF (109/646 Pages) Microchip Technology – 64/100-Pin General Purpose and USB 32-Bit Flash Microcontrollers

6.5 Program Flash Memory Wait
States
For optimal performance, PFMWS(CHECON<2:0>)
must be programmed to the minimum value possible.
There are two parameters that determine this value:
Flash Access Time – The Flash access time is
33 nSec for the PIC32MX3XX/4XX processor family.
CPU Core frequency – The Core frequency is
programmable. Care must be taken when changing fre-
quencies to make sure that there are enough Wait
states to prevent any Flash memory access timing
violations.
To determine the required number of Wait states for a
particular core clock frequency, refer to Table 30-11 in
Section 30.0 “Electrical Characteristics” of this data
sheet.
PIC32MX3XX/4XX
6.6 Program Flash Memory
Partitioning
The Program Flash Memory can be partitioned for User
and Kernel mode programs as shown in Figure 6-3.
At Reset, the User mode partition does not exist
(BMX-PUPBA is initialized to ‘0’). The entire Program
Flash Memory is mapped to Kernel mode program
space starting at virtual address KSEG1: 0xBD000000
(or KSEG0: 0x9D000000). To set up a partition for the
User mode program, initialize BMXPUPBA as follows:
BMXPUPBA = BMXPFMSZ – USER_FLASH_PGM_SZ
The USER_FLASH_PGM_SZ is the partition size of
the User mode program. BMXPFMSZ is the bus matrix
register that holds the total size of Program Flash
Memory.
Example:
Assuming the PIC32MX3XX/4XX device has
512 Kbytes of Flash memory, the BMXPFMSZ will
contain 0x00080000.
To create a user Flash program partition of
20 Kbytes (0x5000):
BMXPUPBA = 0x80000 – 0x5000 = 0x7B000
The size of the user Flash will be 20K and the size left
for the kernel Flash will be 512k – 20k = 492K.
The user Flash partition will extend from 0x7D07B000
to 0x7D07FFFF (virtual addresses).
The Kernel mode partition always starts from KSEG1:
0xBD000000 or KSEG0: 0x9D000000. In the above
example, the kernel partition will extend from
0xBD000000 to 0xBD07AFFF (492 Kbytes in size).
© 2008 Microchip Technology Inc.
Preliminary
DS61143E-page 107