PIC18F2450-I/ML Microchip Technology Inc., PIC18F2450-I/ML Datasheet - Page 75

• Manufacturer Part Number: PIC18F2450-I/ML
• Description: Microcontroller; 16 KB Flash; 768 RAM; 0 EEPROM; 23 I/O; 28-Pin-QFN
• Manufacturer: Microchip Technology Inc.

Specifications of PIC18F2450-I/ML

• A/d Inputs: 10-Channel, 10-Bit
• Cpu Speed: 12 MIPS
• Eeprom Memory: 0 Bytes
• Input Output: 23
• Interface: EUSART/USB
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 28-pin QFN
• Programmable Memory: 16K Bytes
• Ram Size: 768 Bytes
• Speed: 48 MHz
• Timers: 1-8-bit, 2-16-bit
• Voltage, Range: 2-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

6.0
The Flash program memory is readable, writable and
erasable, during normal operation over the entire V
range.
A read from program memory is executed on one byte
at a time. A write to program memory is executed on
blocks of 16 bytes at a time. Program memory is
erased in blocks of 64 bytes at a time. A Bulk Erase
operation may not be issued from user code.
Writing or erasing program memory will cease
instruction fetches until the operation is complete. The
program memory cannot be accessed during the write
or erase, therefore, code cannot execute. An internal
programming timer terminates program memory writes
and erases.
A value written to program memory does not need to be
a valid instruction. Executing a program memory
location that forms an invalid instruction results in a
NOP.
FIGURE 6-1:
© 2006 Microchip Technology Inc.
Note 1:
TBLPTRU
FLASH PROGRAM MEMORY
Table Pointer register points to a byte in program memory.
Table Pointer
TBLPTRH
TABLE READ OPERATION
(1)
TBLPTRL
Program Memory
(TBLPTR)
Advance Information
DD
Instruction: TBLRD*
Program Memory
6.1
In order to read and write program memory, there are
two operations that allow the processor to move bytes
between the program memory space and the data RAM:
• Table Read (TBLRD)
• Table Write (TBLWT)
The program memory space is 16 bits wide, while the
data RAM space is 8 bits wide. Table reads and table
writes move data between these two memory spaces
through an 8-bit register (TABLAT).
Table read operations retrieve data from program
memory and place it into the data RAM space.
Figure 6-1 shows the operation of a table read with
program memory and data RAM.
Table write operations store data from the data memory
space into holding registers in program memory. The
procedure to write the contents of the holding registers
into program memory is detailed in Section 6.5 “Writing
to Flash Program Memory”. Figure 6-2 shows the
operation of a table write with program memory and data
RAM.
Table operations work with byte entities. A table block
containing data, rather than program instructions, is not
required to be word-aligned. Therefore, a table block can
start and end at any byte address. If a table write is being
used to write executable code into program memory,
program instructions will need to be word-aligned.
Table Reads and Table Writes
PIC18F2450/4450
Table Latch (8-bit)
TABLAT
DS39760A-page 73