DV164101 Microchip Technology, DV164101 Datasheet - Page 64

• Manufacturer Part Number: DV164101
• Description: KIT DEV PICKIT1 FLASH 8/14PIN
• Manufacturer: Microchip Technology
• Series: PICkit™ 1r
• Type: MCUr

Specifications of DV164101

• Contents: PIC Kit 1 Circuit Board, CD-ROMs, USB Interface Cable and Booklet
• Processor To Be Evaluated: PIC12F675
• Interface Type: USB
• Silicon Manufacturer: Microchip
• Core Architecture: PIC
• Core Sub-architecture: PIC12, PIC16
• Silicon Core Number: PIC12F, PIC16F
• Silicon Family Name: PIC12F6xx, PIC16F6xx
• Rohs Compliant: NA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: Microchip's 8-14 Pin FLASH Microcontrollers
• For Use With: AC164122 - BOARD DAUGHT PICTAIL SD/MMC CARDAC164120 - BOARD SIGNAL ANALYSIS PICKIT
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: DV164101R; DV164101R

PICkit
C.7
DS40051D-page 60
LESSON 5 – PROGRAM MEMORY LOOK-UP ROUTINES
™
1 Flash Starter Kit User’s Guide
There is often a need to store constants or strings in a PIC microcontroller. Storing this
information in program memory is the best solution as long as this data never needs to
change and program memory is available. Program memory is non-volatile, therefore,
it will maintain information regardless of V
This lesson demonstrates how to retrieve data from Program Memory. It covers the
following topics:
• What a program memory look-up table is
• How a program memory look-up table is implemented
• Why a program memory look-up table is useful
C.7.1
Constants stored in program memory are accessed via look-up tables. A look-up table
is similar to a computed goto (see Lesson 2) only instead of a list of goto statements,
after incrementing the program counter, there is a list of retlw instructions. Each
retlw instruction is followed by one byte of the information. Example C-3 shows a
look-up table for the string “Microchip” written in assembly language.
EXAMPLE C-3:
For this lesson, constants corresponding to a sequence of LEDs are stored in a
program memory look-up table. For instance, the first constant stored is 5F. This
corresponds to the binary number “01011111”. Each bit corresponds to an LED,
therefore, LEDs D0, D1, D2, D3, D4 and D6 will be lit when this constant is accessed.
After each look-up table, the value is displayed on the LEDs in the same fashion as
discussed in Lesson 3, using the Timer0 interrupt. The appearance of more than one
LED being lit at a time is possible because the LEDs are multiplexed fast enough that
the human eye can not detect the LEDs being turned on and off. When SW1 is pressed,
an interrupt-on-change is generated to increment the lookup to the next location.
Figure C-14 shows the flowchart for this example.
LookupProgramMemory
StartTable
movlw
movwf
movlw
addwf
btfsc
incf
movwf
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
retlw
Design
high StartTable
PCLATH
low StartTable
index, w
STATUS, C
PCLATH, f
PCL
"
"
"c"
"r"
"o"
"c"
"h"
"i"
"p"
M
i
LOOK-UP TABLE WRITTEN IN ASSEMBLY
"
"
DD
voltage levels or PIC microcontroller reset.
 2004 Microchip Technology Inc.