PIC16F72SLASHML datasheet(29/136 Pages) MICROCHIP

29 / 136 page

 2002 Microchip Technology Inc.

DS39597B-page 27

PIC16F72

4.0

READING PROGRAM MEMORY

The FLASH Program Memory is readable during nor-

mal operation over the entire VDD range. It is indirectly

addressed through Special Function Registers (SFR).

Up to 14-bit wide numbers can be stored in memory for

use as calibration parameters, serial numbers, packed

7-bit ASCII, etc. Executing a program memory location

containing data that forms an invalid instruction results

in a NOP.

There are five SFRs used to read the program and

memory:

• PMCON1

• PMDATL

• PMDATH

• PMADRL

• PMADRH

The program memory allows word reads. Program

memory access allows for checksum calculation and

reading calibration tables.

When interfacing to the program memory block, the

PMDATH:PMDATL registers form a two-byte word,

which

holds

the

14-bit

data

for

reads.

The

PMADRH:PMADRL registers form a two-byte word,

which holds the 13-bit address of the FLASH location

being accessed. This device has up to 2K words of

program FLASH, with an address range from 0h to

07FFh. The unused upper bits PMDATH<7:6> and

PMADRH<7:5> are not implemented and read as

zeros.

4.1

PMADR

The address registers can address up to a maximum of

8K words of program FLASH.

When selecting a program address value, the MSByte

of the address is written to the PMADRH register and

the LSByte is written to the PMADRL register. The

upper MSbits of PMADRH must always be clear.

4.2

PMCON1 Register

PMCON1 is the control register for memory accesses.

The control bit RD initiates read operations. This bit

cannot be cleared, only set, in software. It is cleared in

hardware at the completion of the read operation.

PMCON1: PROGRAM MEMORY CONTROL REGISTER 1 (ADDRESS 18Ch)

R-1

U-0

R/S-0

reserved

—

bit 7

bit 0

bit 7

Reserved: Read as ‘1’

bit 6-1

Unimplemented: Read as ‘0’

bit 0

RD: Read Control bit

= Initiates a FLASH read, RD is cleared in hardware. The RD bit can only be set (not cleared)

in software.

= Does not initiate a FLASH read

Legend:

W = Writable bit

U = Unimplemented bit, read as ‘0’

R = Readable bit

S = Settable bit

-n = Value at POR

‘1’ = Bit is set

‘0’ = Bit is cleared

x = Bit is unknown

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