PIC16F72 datasheet(38/136 Pages) MICROCHIP

38 / 136 page

PIC16F72

DS39597C-page 36

7.3

Reading the FLASH Program

Memory

To read a program memory location, the user must

write two bytes of the address to the PMADRL and

PMADRH registers and then set control bit, RD

(PMCON1<0>). Once the read control bit is set, the

program memory FLASH controller will use the second

instruction cycle after to read the data. This causes the

second instruction immediately following the “BSF

PMCON1,RD

” instruction to be ignored. The data is

available in the very next cycle in the PMDATL and

PMDATH registers; therefore, it can be read as two

bytes in the following instructions. PMDATL and

PMDATH registers will hold this value until another

read, or until it is written to by the user (during a write

operation).

7.4

Operation During Code Protect

The FLASH program memory control can read any-

where within the program memory, whether or not the

program memory is code protected.

This does not compromise the code, because there is

no way to rewrite a portion of the program memory, or

leave contents of a program memory read in a register

while changing modes.

EXAMPLE 7-1:

FLASH PROGRAM READ

TABLE 7-1:

REGISTERS ASSOCIATED WITH PROGRAM FLASH

BANKSEL PMADRH

; Select Bank for PMADRH

MOVLW

MS_PROG_EE_ADDR

;

MOVWF

PMADRH

; MS Byte of Program Address to read

MOVLW

LS_PROG_EE_ADDR

;

MOVWF

PMADRL

; LS Byte of Program Address to read

BANKSEL PMCON1

; Select Bank for PMCON1

BSF

PMCON1, RD

; EE Read

;

NOP

; Any instructions here are ignored as program

NOP

; memory is read in second cycle after BSF PMCON1,RD

;

; First instruction after BSF PMCON1,RD executes normally

BANKSEL PMDATL

; Select Bank for PMDATL

MOVF

PMDATL, W

; W = LS Byte of Program PMDATL

MOVF

PMDATH, W

; W = MS Byte of Program PMDATL

Address

Name

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

Value on

POR, BOR

Value on

all other

RESETS

10Dh

PMADRL

Address Register Low Byte

xxxx xxxx uuuu uuuu

10Fh

PMADRH

—

Address Register High Byte

xxxx xxxx uuuu uuuu

10Ch

PMDATL

Data Register Low Byte

xxxx xxxx uuuu uuuu

10Eh

PMDATH

—

Data Register High Byte

xxxx xxxx uuuu uuuu

18Ch

PMCON1

—(1)

—

1--- ---0 1--- ---0

Legend: x = unknown, u = unchanged, r = reserved, - = unimplemented, read as '0'.

Shaded cells are not used during FLASH access.

Note 1: This bit always reads as a ‘1’.

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