PIC16F874 datasheet(3/22 Pages) MICROCHIP

3 / 22 page

 2002 Microchip Technology Inc.

DS39025F-page 3

PIC16F87X

2.0

PROGRAM MODE ENTRY

2.1

User Program Memory Map

The user memory space extends from 0x0000 to

0x1FFF (8K). In Programming mode, the program

memory space extends from 0x0000 to 0x3FFF, with

the first half (0x0000-0x1FFF) being user program

memory and the second half (0x2000-0x3FFF) being

configuration memory. The PC will increment from

0x0000 to 0x1FFF and wrap to 0x0000, 0x2000 to

0x3FFF and wrap around to 0x2000 (not to 0x0000).

Once in configuration memory, the highest bit of the PC

stays a ‘1’, thus always pointing to the configuration

memory. The only way to point to user program mem-

ory is to reset the part and re-enter Program/Verify

mode, as described in Section 2.4.

In the configuration memory space, 0x2000-0x200F

are physically implemented. However, only locations

0x2000 through 0x2007 are available. Other locations

are reserved. Locations beyond 0x200F will physically

access user memory (see Figure 2-1).

2.2

Data EEPROM Memory

The EEPROM data memory space is a separate block

of high endurance memory that the user accesses

using a special sequence of instructions. The amount

of data EEPROM memory depends on the device and

is shown below in number of bytes.

The contents of data EEPROM memory have the capa-

bility to be embedded into the HEX file.

The programmer should be able to read data EEPROM

information from a HEX file and conversely (as an

option), write data EEPROM contents to a HEX file,

along with program memory information and configura-

tion bit information.

The 256 data memory locations are logically mapped

starting at address 0x2100. The format for data mem-

ory storage is one data byte per address location, LSB

aligned.

2.3

ID Locations

A user may store identification information (ID) in four

ID locations. The ID locations are mapped in [0x2000 :

0x2003]. It is recommended that the user use only the

four Least Significant bits of each ID location. In some

devices, the ID locations read out in an unscrambled

fashion after code protection is enabled. For these

devices, it is recommended that ID location is written as

“11 1111 1000 bbbb” where ‘bbbb’ is ID information.

In other devices, the ID locations read out normally,

even after code protection. To understand how the

devices behave, refer to Table 5-1.

To understand the scrambling mechanism after code

protection, refer to Section 4.0.

Device

# of Bytes

PIC16F870

PIC16F871

PIC16F872

PIC16F873

128

PIC16F874

128

PIC16F876

256

PIC16F877

256

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