Supported by A/D chip or internal A/D converter.

Characterized by:
1. Resolution – the minimum change in input voltage that can give rise to a change in output
Resolution = (VRH – VRL) / (# of quantization steps) # of quantization steps = 2^b where b is # bits used for encoding

2. Linearity – higher for a better conversion

3. Speed
Need data rate to satisfy the Nyquist criterion.
Recall that Nyquist criterion says sampling frequency should be at least twice the frequency of the fastest harmonic of the signal to be sampled.

Popularity: 7%

A seven segment LED consist of seven light emitting diode segments and one segment for the decimal point. The segments are physically arranged in the form of 8.

To display a number , or a letter from A to F the necessary segments are lit by sending an appropriate signal for current flow through the diodes.

An LED will be illuminated if it is forward-biased and there is enough current flowing through it.

Typically, a current of few milliamps up to 20mA is required.

The voltage drop across a forward-biased LED ranges from about 1.6V to 2.5V.

The 7 segment LEDs are available in two types:
i) common cathode
ii) common anode.

The current flow in these diodes should be limited to 20 ma. The segments A through G are are usually connected to data lines D0 through D6 respectively. If the decimal point is used the data line D7 is connected to the decimal point, otherwise it is left open.

The binary code required to to display a digit is determined by the type of LED configuration ( common anode or common cathode)

For common anode configuration a logic 0 is required to turn on a segment. For common cathode type a logic 1 is required.

With displays having many display elements, rather than having to use a decoder for each element, multiplexing is used with a single decoder.

To maintain a constant display, a display is repeatedly turned on sufficiently often for the display to appear flicker-free.

Popularity: 8%

Multiple data, control, and possibly power wires

One bit per wire

High data throughput with short distances

Typically used when connecting devices on same IC or same circuit board

Bus must be kept short

long parallel wires result in high capacitance values which requires more time to charge/discharge

Data misalignment between wires increases as length increases

Higher cost, bulky

Popularity: 7%

Single data wire, possibly also control and power wires

Words transmitted one bit at a time

Higher data throughput with long distances

Less average capacitance, so more bits per unit of time

Cheaper, less bulky

More complex interfacing logic and communication protocol

Sender needs to decompose word into bits

Receiver needs to recompose bits into word

Control signals often sent on same wire as data increasing protocol complexity

Popularity: 7%

Peripheral devices (also called I/O devices) are pieces of equipment that exchange data with a CPU

Examples: switches, LED, CRT, printers, keyboard, keypad

Speed and characteristics of these devices are very different from that of CPU so they cannot be connected directly

Interface chips are needed to resolve this problem

Main function of an interface chip is to synchronize data transfer between CPU and I/O device

Data pins of interface chip are connected to CPU data bus and I/O port pins are connected to I/O device

Since a CPU may have multiple I/O devices, CPU data bus may be connected to data buses of multiple interface

An address decoder is used to select one device to respond to the CPU I/O request

Different CPUs deal with I/O devices differently
Some CPUs have dedicated instructions for performing input and output operations (isolated I/O)

Other CPUs use the same instruction for reading from memory and reading from input devices, as well as writing data into memory and writing data into output devices (memory-mapped I/O)
8051 is memory mapped

Popularity: 7%

Fet89c5x Programmer Download

Best 8051 compiler software to use. Works with all kinds of 8051 microcontroller.

Compile 8051 asm to hex.

Popularity: 10%

Edsim51 another great simulator for your 8051 microcontroller.

This program works in Win9x,XP,NT,Vista.

A great interface simulator for 8051.

Tutorial are provided with the program.

100% Free to Download

Popularity: 14%

This 8051 asm source code can be simulated using simulator Edsim51

; This program multiplexes the number 1234
; on the four 7-segment displays.
; Note: a logic 0 lights a display segment.

start:
SETB P3.3 ; |
SETB P3.4 ; | enable display 3
MOV P1, #11111001B ; put pattern for 1 on display
MOV P1, #0FFH ; clear the display
CLR P3.3 ; enable display 2
MOV P1, #10100100B ; put pattern for 2 on display
MOV P1, #0FFH ; clear the display
CLR P3.4 ; |
SETB P3.3 ; | enable display 1
MOV P1, #10110000B ; put pattern for 3 on display
MOV P1, #0FFh ; clear the display
CLR P3.3 ; enable display 0
MOV P1, #10011001B ; put pattern for 4 on display
MOV P1, #0FFH ; clear display
JMP start ; jump back to start

Popularity: 25%