DV164136 Microchip Technology, DV164136 Datasheet - Page 71

• Manufacturer Part Number: DV164136
• Description: DEVELOPMENT KIT FOR PIC18
• Manufacturer: Microchip Technology
• Series: PIC®r
• Type: MCUr

Specifications of DV164136

• Contents: Board, Cables, CDs, PICkit™ 3 Programmer, Power Supply
• Processor To Be Evaluated: PIC18F8722, PIC18F87J11
• Interface Type: RS-232, USB
• Operating Supply Voltage: 3.3 V, 5 V
• Silicon Manufacturer: Microchip
• Core Architecture: PIC
• Core Sub-architecture: PIC18
• Silicon Core Number: PIC18F
• Silicon Family Name: PIC18F8xxx
• Kit Contents: PIC18 Exp Brd PICkit 3 Cable CD PSU
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: PIC18F8722, PIC18F87J11
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

5.2.3
The program memory is addressed in bytes. Instruc-
tions are stored as two bytes or four bytes in program
memory. The Least Significant Byte of an instruction
word is always stored in a program memory location
with an even address (LSB = 0). To maintain alignment
with instruction boundaries, the PC increments in steps
of 2 and the LSB will always read ‘0’ (see Section 5.1.5
“Program Counter”).
Figure 5-6 shows an example of how instruction words
are stored in the program memory.
FIGURE 5-6:
5.2.4
The standard PIC18 instruction set has four two-word
instructions: CALL, MOVFF, GOTO and LSFR. In all
cases, the second word of the instructions always has
‘1111’ as its four Most Significant bits; the other 12 bits
are literal data, usually a data memory address.
The use of ‘1111’ in the 4 MSbs of an instruction
specifies a special form of NOP. If the instruction is
executed in proper sequence – immediately after the
first word – the data in the second word is accessed
EXAMPLE 5-4:
© 2009 Microchip Technology Inc.
CASE 1:
Object Code
CASE 2:
Object Code
0110 0110 0000 0000
1100 0001 0010 0011
1111 0100 0101 0110
0010 0100 0000 0000
0110 0110 0000 0000
1100 0001 0010 0011
1111 0100 0101 0110
0010 0100 0000 0000
INSTRUCTIONS IN PROGRAM
MEMORY
TWO-WORD INSTRUCTIONS
Instruction 1:
Instruction 2:
Instruction 3:
INSTRUCTIONS IN PROGRAM MEMORY
TWO-WORD INSTRUCTIONS
Program Memory
Byte Locations
MOVLW
GOTO
MOVFF
Source Code
TSTFSZ
Source Code
MOVFF
ADDWF
TSTFSZ
MOVFF
ADDWF
055h
0006h
123h, 456h
→
REG1
REG1, REG2
REG3
REG1
REG1, REG2
REG3
LSB = 1
; is RAM location 0?
; No, skip this word
; Execute this word as a NOP
; continue code
; is RAM location 0?
; Yes, execute this word
; 2nd word of instruction
; continue code
EFh
C1h
0Fh
F0h
F4h
PIC18F87J11 FAMILY
The CALL and GOTO instructions have the absolute
program memory address embedded into the instruc-
tion. Since instructions are always stored on word
boundaries, the data contained in the instruction is a
word address. The word address is written to PC<20:1>
which accesses the desired byte address in program
memory. Instruction #2 in Figure 5-6 shows how the
instruction, GOTO 0006h, is encoded in the program
memory. Program branch instructions, which encode a
relative address offset, operate in the same manner. The
offset value stored in a branch instruction represents the
number of single-word instructions that the PC will be
offset by. Section 25.0 “Instruction Set Summary”
provides further details of the instruction set.
and used by the instruction sequence. If the first word
is skipped for some reason and the second word is
executed by itself, a NOP is executed instead. This is
necessary for cases when the two-word instruction is
preceded by a conditional instruction that changes the
PC. Example 5-4 shows how this works.
Note:
LSB = 0
55h
03h
00h
23h
56h
See Section 5.5 “Program Memory and
the Extended Instruction Set” for
information on two-word instructions in the
extended instruction set.
Word Address
00000Ah
00000Ch
00000Eh
000000h
000002h
000004h
000006h
000008h
000010h
000012h
000014h
↓
DS39778D-page 71