1. PIC Microcontroller
What is PC LATH?????

2. Memory Classification
Program Memory
(Flash)
Data Memory
General Purpose
RAM
Special Function
Registers

3. Program Memory Organization
8k x 14 program memory space
Divided into 4 pages of 2k words each
0H to 7FFH
800H to FFFH
1000H to 17FFH
1800H to 1FFFH
Program PCLATH to switch between pages

4. Program Memory Organization
PCLATH<4:3> = 00
PCLATH<4:3> = 10
Reset
0000h
Page 2
1000h
0004h
Interrupt
Page 0
07FFh
17FFh
PCLATH<4:3> = 01
PCLATH<4:3> = 11
Reset vector at 0, Interrupt vector at 4h
In 2K Program memory, PCLATH has no impact
In 4K Program memory, PCLATH bit 3 selects 2K page. Since PCLATH is not ininialized on reset (POR or otherwise), user must initialize PCLATH after reset.
Page 1
0800h
Page 3
1800h
0FFFh
1FFFh

5. Program Memory Map

6. Vectors Reset Vector Interrupt Vector Reset forces PC to 0x0000 H
Clears the PCLATH So?
Interrupt Vector
Interrupt forces PC to 0x0004 H
PCLATH is not modified

7. Program Counter PC is 13 bits wide
Low byte – PCL is readable & writable
High byte – PCH is not directly readable or writable
All updates to PCH goes through PCLATH

8. Program Counter

11. Program Counter

12. Stack 8 level deep x 13 bit wide
Not part of either program space or data space
Stack pointer is not readable or writable

13. Stack PCLATH is not modified with a stack operation
No status bits to indicate status overflow or underflow conditions
No instructions called PUSH or POP