PIC16F818/819
2.0
MEMORY ORGANIZATION
2.1
Program Memory Organization
There are two memory blocks in the PIC16F818/819.
These are the program memory and the data memory.
Each block has its own bus, so access to each block
can occur during the same oscillator cycle.
The data memory can be further broken down into the
general purpose RAM and the Special Function
Registers (SFRs). The operation of the SFRs that
control the “core” are described here. The SFRs used
to control the peripheral modules are described in the
section discussing each individual peripheral module.
The data memory area also contains the data
EEPROM memory. This memory is not directly mapped
into the data memory but is indirectly mapped. That is,
an indirect address pointer specifies the address of the
data EEPROM memory to read/write. The PIC16F818
device’s 128 bytes of data EEPROM memory have the
address range of 00h-7Fh and the PIC16F819 device’s
256 bytes of data EEPROM memory have the address
range of 00h-FFh. More details on the EEPROM
memory can be found in
Additional information on device memory may be found
in the
“PICmicro
®
Mid-Range Reference Manual”
(DS33023).
The PIC16F818/819 devices have a 13-bit program
counter capable of addressing an 8K x 14 program
memory space. For the PIC16F818, the first 1K x 14
(0000h-03FFh) is physically implemented (see
located at 0000h-07FFh (see Figure 2-2). Accessing a
location above the physically implemented address will
cause a wraparound. For example, the same instruc-
tion will be accessed at locations 020h, 420h, 820h,
C20h, 1020h, 1420h, 1820h and 1C20h.
The Reset vector is at 0000h and the interrupt vector is
at 0004h.
FIGURE 2-1:
PROGRAM MEMORY MAP
AND STACK FOR
PIC16F818
PC<12:0>
FIGURE 2-2:
PROGRAM MEMORY MAP
AND STACK FOR
PIC16F819
PC<12:0>
CALL, RETURN
RETFIE, RETLW
13
CALL, RETURN
RETFIE, RETLW
13
Stack Level 1
Stack Level 2
Stack Level 1
Stack Level 2
Stack Level 8
Reset Vector
0000h
Stack Level 8
Reset Vector
0000h
Interrupt Vector
On-Chip
Program
Memory
Page 0
0004h
0005h
03FFh
0400h
Interrupt Vector
On-Chip
Program
Memory
0004h
0005h
Page 0
07FFh
0800h
Wraps to
0000h-03FFh
Wraps to
0000h-07FFh
1FFFh
1FFFh
2004 Microchip Technology Inc.
DS39598E-page 9
MICROCHIP [ MICROCHIP TECHNOLOGY ]
