PIC32MX575F256LT-80I/PT Microchip Technology, PIC32MX575F256LT-80I/PT Datasheet - Page 39

• Manufacturer Part Number: PIC32MX575F256LT-80I/PT
• Description: 256KB Flash, 64KB RAM, 80 MHz, USB, 1xCAN, 8 DMA 100 TQFP 12x12x1mm T/R
• Manufacturer: Microchip Technology
• Series: PIC® 32MXr

Specifications of PIC32MX575F256LT-80I/PT

• Core Processor: MIPS32® M4K™
• Core Size: 32-Bit
• Speed: 80MHz
• Connectivity: CAN, I²C, SPI, UART/USART, USB OTG
• Peripherals: Brown-out Detect/Reset, DMA, POR, PWM, WDT
• Number Of I /o: 85
• Program Memory Size: 256KB (256K x 8)
• Program Memory Type: FLASH
• Ram Size: 64K x 8
• Voltage - Supply (vcc/vdd): 2.3 V ~ 3.6 V
• Data Converters: A/D 16x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 100-TFQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

17.3
An example of a high-level algorithm for calculating the
checksum for a PIC32 device is illustrated in Figure 17-1
to demonstrate one method to derive a checksum. This
is merely an example of how the actual calculations can
be accomplished, the method that is ultimately used is
left to the discretion of the software developer.
As stated earlier, the PIC32 checksum is calculated as
the 32-bit summation of all bytes (8-bit quantities) in
program
Configuration Words), the Device ID register with
applicable mask, and the device Configuration Words
with applicable masks.
FIGURE 17-1:
© 2010 Microchip Technology Inc.
Read Program Flash, Boot Flash (including DEVCFG
Algorithm
Apply DEVCFG and DEVID masks to appropriate
Checksum (32-bit quantity) = 2’s complement
Flash,
registers) and DEVID register in tempBuffer
tmpChecksum (32-bit quantity) = 0
bytes (8-bit quantities) in
locations in tempBuffer
boot
Finish processing all
HIGH-LEVEL ALGORITHM FOR CHECKSUM CALCULATION
pic32_checksum
of tmpChecksum
tempBuffer?
Flash
Done
Yes
(except
device
No
tmpChecksum = tempChecksum + Current Byte Value
Next, the 2’s complement of the summation is
calculated. This final 32-bit number is presented as the
checksum.
The mask values of the device Configuration and
Device ID registers are derived as described in the
previous section, 17.2 “Mask Values”.
Another noteworthy point is that the last four 32-bit
quantities in boot Flash are the device Configuration
registers. An arithmetic AND operation of these device
Configuration register values is performed with the
appropriate mask value, before adding their bytes to
the checksum.
Similarly, an arithmetic AND operation of the Device ID
register is performed with the appropriate mask value,
before adding its bytes to the checksum.
(8-bit quantity) in tmpBuffer
PIC32MX
DS61145G-page 39