PIC16C925T-S/CL 查看數據表（PDF） - Microchip Technology

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PIC16C925T-S/CL

64/68-Pin CMOS Microcontrollers with LCD Driver

Microchip Technology 

PIC16C925/926

3.3 Reading the Program Memory

A program memory location may be read by writing two

bytes of the address to the PMADR and PMADRH reg-

isters, and then setting control bit RD (PMCON1<0>).

Once the read control bit is set, the microcontroller will

use the next two instruction cycles to read the data. The

data is available in the PMDATA and PMDATH regis-

ters after the NOP instruction. Therefore, it can be read

as two bytes in the following instructions. The PMDATA

and PMDATH registers will hold this value until another

read operation.

EXAMPLE 3-1: PROGRAM READ

BSF

STATUS, RP1

BSF

STATUS, RP0

MOVLW MS_PROG_PM_ADDR

MOVWF PMADRH

MOVLW LS_PROG_PM_ADDR

MOVWF PMADR

BCF

STATUS, RP0

BSF

PMCON1, RD

;

BSF

;

NOP

STATUS, RP0

;

MOVF

MOVF

PMDATA, W

PMDATH, W

;

; Bank 3

;

; MS Byte of Program Address to read

;

; LS Byte of Program Address to read

; Bank 2

; PM Read

; First instruction after BSF PMCON1,RD executes normally

; Bank 3

; Any instructions here are ignored as program

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

; W = LS Byte of Program PMDATA

; W = MS Byte of Program PMDATA

3.4 Operation During Code Protect

If the program memory is not code protected, the pro-

gram memory control can read anywhere within the

program memory.

If the entire program memory is code protected, the

program memory control can read anywhere within the

program memory.

If only part of the program memory is code protected,

the program memory control can read the unprotected

segment and cannot read the protected segment. The

protected area cannot be read, because it may be

possible to write a downloading routine into the

unprotected segment.

TABLE 3-1: REGISTERS ASSOCIATED WITH PROGRAM MEMORY

Address Name

Bit 7

Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1

10Ch

PMCON1

(1)

—

—

—

—

—

—

18Ch

PMDATA Data Register Low Byte

18Dh

18Eh

PMADR Address Register Low Byte

PMDATH

—

— Data Register High Byte

18Fh

PMADRH

—

—

— Address Register High Byte

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’.

Bit 0

RD

Value on:

POR, BOR

Value on

all other

RESETS

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

xxxx xxxx uuuu uuuu

xxxx xxxx uuuu uuuu

xxxx xxxx uuuu uuuu

xxxx xxxx uuuu uuuu

DS39544A-page 28

Preliminary

 2001 Microchip Technology Inc.

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