28123 Parallax Inc, 28123 Datasheet - Page 280

• Manufacturer Part Number: 28123
• Description: TEXT WHAT'S A MICROCONTROLLER
• Manufacturer: Parallax Inc
• Type: Programmingr

Specifications of 28123

• Style: Book
• Title: What's a Microcontroller?
• Contents: Whats a Microcontroller? Text
• Product: Microcontroller Accessories
• Core Processor: PIC16C57c
• Flash: 128 Bytes
• Operating Supply Voltage: 9 V
• Board Size: 31 mm x 16 mm
• Lead Free Status / RoHS Status: Not applicable / Not applicable

LOW 5
DO
LOOP
Looking Inside the Digital Potentiometer
Figure 9-8 shows a diagram of the potentiometer inside the AD5220. The AD5220 has
128 resistive elements, each of which is 78.125 Ω (nominal value). All 128 of these add
up to 10,000 Ω or 10 kΩ.
Between each of these resistive elements is a switch, called a tap. Each switch is actually
a group of transistors that are switched on or off to let current pass or not pass. Only one
of these switches can be closed at one time. If one of the upper switches is closed (like
pos. 125, 126, or 127), it’s like having the manual potentiometer knob turned most or all
the way clockwise. If pos. 0 or 1 is closed, it’s like having a manual potentiometer turned
most or all the way counterclockwise.
FOR counter = 0 TO 127
NEXT
TOGGLE 5
PULSOUT 6,5
PAUSE 10
1 CLK
2 U/D
5
7 CS
A nominal value means a named value. Parts like resistors and capacitors typically have a
nominal value and a tolerance. Each of the AD5220’s resistive elements has a nominal
value of 78.125 Ω, with a tolerance of 30% (23.438 Ω) above or below the nominal value.
W1
Ad5220
40
Ω
pos. 127
pos. 126
pos. 125
pos. 1
pos. 0
…
…
3
6
78
78
78
78
78
A1
B1
Ω
Ω
Ω
Ω
Ω
Figure 9-8
Inside the AD5220