ATMEGA169P-16MCHR【PDF 70/274 页】MCU AVR 16KB FLASH 16MHZ 64-VQFN

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Sheet目录3753

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2005 Microchip Technology Inc.

Preliminary

DS41265A-page 159

PIC16F946

13.0

DATA EEPROM AND FLASH

PROGRAM MEMORY

CONTROL

Data EEPROM memory is readable and writable and

the Flash program memory is readable during normal

operation (full VDD range). These memories are not

directly mapped in the register file space. Instead, they

are indirectly addressed through the Special Function

Registers. There are six SFRs used to access these

memories:

EECON1

EECON2

EEDATL

EEDATH

EEADRL

EEADRH

When interfacing the data memory block, EEDATL

holds the 8-bit data for read/write, and EEADRL holds

the address of the EE data location being accessed.

This device has 256 bytes of data EEPROM with an

address range from 0h to 0FFh.

When interfacing the program memory block, the

EEDATL and EEDATH registers form a 2-byte word

that holds the 14-bit data for read, and the EEADRL

and EEADRH registers form a 2-byte word that holds

the 13-bit address of the EEPROM location being

accessed. This device has 4k and 8k words of program

EEPROM with an address range from 0h-0FFFh and

0h-1FFFh. The program memory allows one-word

reads.

The EEPROM data memory allows byte read and write.

A byte write automatically erases the location and

writes the new data (erase before write).

The write time is controlled by an on-chip timer. The

write/erase voltages are generated by an on-chip

charge pump rated to operate over the voltage range of

the device for byte or word operations.

When the device is code-protected, the CPU may

continue to read and write the data EEPROM memory

and read the program memory. When code-protected,

the device programmer can no longer access data or

program memory.

Additional information on the data EEPROM is

available in the “PICmicro Mid-Range MCU Family

Reference Manual” (DS33023).

13.1

EEADRL and EEADRH Registers

The EEADRL and EEADRH registers can address up

to a maximum of 256 bytes of data EEPROM or up to a

maximum of 8k words of program EEPROM.

When selecting a program address value, the MSB of

the address is written to the EEADRH register and the

LSB is written to the EEADRL register. When selecting

a data address value, only the LSB of the address is

written to the EEADRL register.

13.1.1

EECON1 AND EECON2 REGISTERS

EECON1 is the control register for EE memory

accesses.

Control bit EEPGD determines if the access will be a

program or data memory access. When clear, as it is

when reset, any subsequent operations will operate on

the data memory. When set, any subsequent operations

will operate on the program memory. Program memory

can only be read.

Control bits RD and WR initiate read and write,

respectively. These bits cannot be cleared, only set, in

software. They are cleared in hardware at completion

of the read or write operation. The inability to clear the

WR bit in software prevents the accidental, premature

termination of a write operation.

The WREN bit, when set, will allow a write operation to

data EEPROM. On power-up, the WREN bit is clear.

The WRERR bit is set when a write operation is

interrupted by a MCLR or a WDT Time-out Reset

during normal operation. In these situations, following

Reset, the user can check the WRERR bit and rewrite

the location. The data and address will be unchanged

in the EEDATL and EEADRL registers.

Interrupt flag bit EEIF (PIR1<7>), is set when write is

complete. It must be cleared in the software.

EECON2 is not a physical register. Reading EECON2

will read all ‘0’s. The EECON2 register is used

exclusively in the data EEPROM write sequence.

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