DM164120-2 Microchip Technology, DM164120-2 Datasheet - Page 37

• Manufacturer Part Number: DM164120-2
• Description: BOARD DEMO PICKIT 2 44PIN
• Manufacturer: Microchip Technology
• Type: MCUr

Specifications of DM164120-2

• Contents: 3 Boards (1 Populated, 2 Bare)
• Processor To Be Evaluated: PIC16F
• Silicon Manufacturer: Microchip
• Kit Contents: PIC16F Device, 2 PCB Boards
• Features: Small Surface Mount Prototype Area, Two Bare PCB Boards
• Development Tool Type: Hardware - Daughter Card
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: PIC16F887
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

© 2007 Microchip Technology Inc.
FIGURE 3-12:
This lesson uses the look-up table to implement a binary to Gray code converter. Gray
code is a binary code in which only a single bit changes from one sequence to the next.
They are frequently used in encoder applications to avoid wild jumps between states.
Binary encoders are typically implemented as an opaque disk with slots sensed by light
sensors. Due to different threshold levels on different bits, bits may change at slightly
differently times yielding momentary invalid results. Gray code prevents this because
only one bit changes from one sequence to the next. The current code is correct until
it transitions to the next.
The algorithm to convert between binary and Gray code is fairly complex. For a small
number of bits, the table look-up is smaller and faster.
This lesson takes the Analog-to-Digital value upper nibble and converts it to Gray code
displayed on the first four LEDs. The code changes one bit at a time as the potentiom-
eter rotates across its range (seeExample 3-12).
Gray Code Converter
Decimal
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
PC
Binary
0000
0001
0011
0010
0110
0111
0101
0100
1100
1101
1111
1110
1010
1011
1001
1000
12
PC LOADING AS DESTINATION OF INSTRUCTION
5
PCH
PCLATH<4:0>
44-Pin Demo Board Lessons
PCLATH
8 7
PCL
8
0
ALU Result
Instruction with
Destination
PCL as
DS41296B-page 33