Types of ROM's

We have been hearing the terms volatile memory and non-volatile memory from our 1st year of college. Here is a brush up of what we have heard so far.
The OTP (one time programmable) are used for firmware applications.
The ROM is also known as the program memory or code memory and RAM is also known as the data memory.
The EEPROM are electrically erasable PROM and needs electrical supply to clear the data.
The UVPROM requires UV light to pass through the window to clear the data.
The FLASH ROM are the advanced ones where data is loaded and retrieved in blocks, where each block is greater than 2 bytes, so the operation is faster in the case of FLASH ROM, whereas in the case of EEPROM data is loaded and retrieved byte by byte so it would take much time to access data when compared to FLASH ROM.

Hectic week approaching...

The rain was troubling me much last month, because of it I had to delay every jobs of mine. I even failed to attend two of my classes at AU PERS center. Those two classes covered array of pointers and structures, It was bad that I missed the classes on array of pointers which was an interesting and tough topic. However I hope I could get my doubts cleared on it. The upcoming week I have one week practicals and I have to complete twenty programs within this week and get it signed from the lab incharge. The twenty programs seems to be pretty tough and time consuming I tried to complete only three and it took me two hours and I spent most of my brain work there, now trying to get some relaxation. Hope that I could complete the programs on time and I also have to prepare for the test after this week on C module. I hope that this week is a hectic one and I have to plan well to face it.

Code snippet for working with an ADC

We have already seen the need for an analog to digital converter and also how the conversion takes place, the below code is used to work with an ADC in my PIC development board where the PIC16F877A senses the input from an ADC through RA0 pin and displays the digital value in the LCD which is connected to PORTD and also send the converted data to PORTB.

#include<16f877a.h>
#use delay(clock=4000000)
#include
#byte portb=0x06
#byte porta=0x05
#byte portd=0x08

int16 temp;

main( )

{

lcd_init( ); //INITIALISE THE LCD ;

set_tris_b(0x00); //PORTB IS CONFIGURED AS A O/P;

set_tris_a(0x01); //PORTA IS CONFIGURED AS A I/P;

set_tris_d(0x00); //PORTD IS CONFIGURED AS A O/P;

setup_adc_ports(ra0_analog);

setup_adc(adc_clock_internal);

set_adc_channel(0);

while(1)

{

temp=read_adc(); //OUTPUT IS STORED IN TEMP;

portb=temp;

lcd_gotoxy(1,1);

printf(lcd_putc,"ADC:%4lx",temp); //DISPLAY ON LCD;

delay_ms(500);

}

}

Here you can see in the code that while configuring the pins of PORTA since we are going to sense the analog input from RA0 we hace configured it as an input (set_tris_a(0x01)).

Analog to digital converter module

We have already seen about the need for analog to digital converters in my previous post. Now let us look into how the analog to digital converter module actually works. The below figure represents the analog to digital converter module.


You can see the input pins where the analog data comes from, which are connected to the inputs of an analog multiplexer. The function of the analog multiplexer is to connect the selected input channel to the holding capacitor. The holding capacitor is connected to the output of the analog multiplexer and when a conversion is initiated, the analog multiplexer disconnects all inputs from the holding capacitor, and the successive approximation converter performs the conversion on the voltage stored on the holding capacitor thus providing a digital value at the output.

The need for Analog to Digital Converters

We have seen the advantages of digital signals over the analog signals in transmission of signals. Microcontrollers are very efficient at processing digital numbers, but they cannot handle analog signals directly. An analog-to-digital converter, converts an analog voltage level to a digital number. The microcontroller can then efficiently process the digital representation of the original analog voltage. By definition, digital numbers are non-fractional whole numbers.
In this example, an input voltage of 2.343 volts is converted to 87. The user’s software can use the value 87 as the representation of the original input voltage. The analog input voltage must be within the valid input range of the A/D for accurate conversion. Hope you would have heard about the quantization process of rounding off and the quantization error. The A/D converter which is having higher resolution gives less quantization errors. Hence a 12-bit converter which has 4096 states is much efficient than a 10-bit converter that has 1024 states.

About 8085 simulator's

If you are a college student in your third year then you can realize how important 'Microprocessor and its Applications' subject is. If you attend any technical HR interview then there is sure questions from this subject. For this subject practical knowledge is much more important than theory knowledge. Learning 8085 microprocessor well forms a good base for learning other microprocessors and microcontrollers. So you should try to learn the instruction set and work with Assembly Language Programming of 8085. Even though you may not have a 8085 kit with you but you can download free 8085 simulators that are available in Internet and go on with writing ALP and executing them. These simulators will surely help you to gain good knowledge in 8085 microprocessor. If you get microprocessor book of Goankar then you will be getting free CD with simulator and you can even get the simulator if you get Bhakshi. Well you can have a good knowledge only if you have interest towards learning it. So create your interest towards microprocessor 8085 and it will surely help you in future while attending interviews.

Day 3 at AU PERS center

The government holidays are affecting my embedded system course at Anna University. I think that this October month is having a lot of government holidays that any other month. Even though I had joined the course at September, but because of these holidays I have completed only 3 classes at Anna University. Well the classes are going on well and my staff is concentrating much on practical knowledge apart from teaching theory well. He has completed till arrays and still there are pointers, functions, structures and unions, files and lots more to go. On day 3 he completed with single dimensional array but when he started with pre increment and post increment operators the classes deviated from arrays and he started to fully explain about those operators with practical examples. Then we came back and the class and it took additionally 20 minutes to get over but it was an interesting session. All the programs were like puzzles and I was wrong with most of my answers but at last understood to an extent. Hope when you take up any C programming classes you can be sure of getting into situations like these so don’t miss any classes.