PIC16F72 Datasheet, PDF (29/136 Pages) Microchip Technology – 28-Pin, 8-Bit CMOS FLASH MCU with A/D Converter

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.
REGISTER 4-1:
PMCON1: PROGRAM MEMORY CONTROL REGISTER 1 (ADDRESS 18Ch)
R-1
U-0
U-0
U-0
U-0
U-0
U-0
R/S-0
reserved
—
—
—
—
—
—
RD
bit 7
bit 0
bit 7
bit 6-1
bit 0
Reserved: Read as ‘1’
Unimplemented: Read as ‘0’
RD: Read Control bit
1 = Initiates a FLASH read, RD is cleared in hardware. The RD bit can only be set (not cleared)
in software.
0 = Does not initiate a FLASH read
Legend:
W = Writable bit
R = Readable bit
‘1’ = Bit is set
U = Unimplemented bit, read as ‘0’
S = Settable bit
-n = Value at POR
‘0’ = Bit is cleared
x = Bit is unknown
 2002 Microchip Technology Inc.
DS39597B-page 27