The document discusses configuring the on-chip analog to digital converter (ADC) on the PIC16F877 microcontroller. It first provides an overview of the PIC microcontroller family and key features of the PIC16F877. It then describes the ADC registers and conversion process, including configuring the ADC module, selecting the input channel, starting the conversion, and reading the result. It includes a diagram of the ADC conversion timing and flowchart of the conversion process. An example code for reading the ADC and printing the result is also provided.

1. CONFIGURING
ON-CHIP ADC
ON PIC 16F877
By
GAURAV .M. RAIKAR
Roll No: EL-18-

2. PIC MICROCONTROLLER
PIC (Peripheral Interface Controller ) is family of microcontrollers made by
“Microchip Technology”.
PIC microcontrollers are very fast and executing a program is easier compared to
other controllers. It follows “Harvard architecture” for internal data transfer. Its
architecture comprises of CPU, RAM, ROM, timers, counters and protocols like
SPI, UART, CAN which are used for interfacing with other peripherals. .
PIC are small microcontroller that can be programmed to carry out a vast range of
tasks. The programming and the simulation process of this microcontroller can be
done using MP-LAB software.
Even though there are many types of PIC microcontrollers , the most widely used
and basic microcontroller is PIC16F877.

3. PIC 16F877 :FEATURES
8 bit microcontroller
8k x 14 words of flash program memory.
368 x 8 bytes of data memory(RAM).
256 x 8 bytes of EEPROM data memory.
20MHz operating speed (200 ns instruction
cycle).
Wide operating voltage range(2.0-5.6)volts.
High Sink/Source current, about 25mA.
Package options(40 or 44 pins).
High performance RISC CPU.
35 simple word Instructions.
Support for 14 interrupts.
Supports different types of addressing modes.
Power up timer(PWRT).
3 timers (Multiple modes 8 bit,16 bit support).
10 bit multi-channel Analog to digital convertor (10 bit
resolution)..
Universal synchronous asynchronous receiver transmitter
(USART).
Supports for I2C.
Supports SPI.
Brown out reset(BOR).
Watch dog timer.

4. PIC microcontroller types

5. Instruction set for PIC 16F877(35 instructions)

6. PIC 16F877 of Architecture

7. Program Memory:
• This is a 8K*14 memory space.
• It contains the programs that are written
by the user.
• The program memory data is accessed
by the 13 bit program counter register
that holds the address of the program
memory.
• The address 0000H is used as reset
memory space and 0004H is used as
interrupt memory space.
The PIC 16F877 consists of 3 memories:
Program memory , Data memory and Data EEPROM.

8. • Data Memory: The data memory
consists of the 368 bytes of RAM
and 256 bytes of EEPROM.
• The Data Memory consists of
multiple banks.
• Each bank consists of general
purpose registers and special
function registers.
• The special function registers
consists of control registers to
control different operations of the
chip resources like Timers, Analog
to Digital Converters, Serial ports,
I/O ports, etc.

9. • Data EEPROM (Electrically Erasable Programmable Read-Only
Memory) - Data EEPROM they are non-volatile memories, which store the
information even after the power is turn off. These memories called Flash Or
EEPROM.
• The general purpose registers -consists of registers that are used to store
temporary data and processing results of the data. These general purpose registers
are each 8-bit registers.
• Working Register -It consists of a memory space that stores the operands for
each instruction. It also stores the results of each execution.
• File Selection Register- It acts as a pointer to any other general-purpose
register. It consists of a register file address, and it is used in indirect addressing.
• Program-counter register- It is a 13-bit register. The 5 upper bits are used as
PCLATH (Program Counter Latch) to independently function as any other
register, and the lower 8-bits are used as the program counter bits. The program
counter acts as a pointer to the instructions stored in the program memory.

10. • Status Register: The bits of the status register denote the status of the ALU (arithmetic logic unit) after every
execution of the instruction. It is also used to select any one of the 4 banks of the RAM.
IRP - Register Bank Select bit, used for indirect addressing method.
When the IRP Equal to 0, the program will work with banks 0, 1.
When the IRP Equal to 1, the program will work with banks 2, 3.
RP1:RP0: - Register Bank Select bits, used for direct addressing method
selection of the RP0 and RP1 bits helps in selecting one of the 4 banks.
C: Carry/borrow bit
1 = A carry-out from the Most Significant bit of the result occurred
0 = No carry-out from the Most Significant bit of the result occurred
DC: Digit carry/borrow bit (for borrow, the polarity is reversed)
1 = A carry-out from the 4th low order bit of the result occurred
0 = No carry-out from the 4th low order bit of the result
Z: Zero bit
1 = The result of an arithmetic or logic operation is zero
0 = The result of an arithmetic or logic operation is not zero
PD: Power-down bit
1 = After power-up or by the CLRWDT instruction
0 = By execution of the SLEEP instruction
TO: Time-out bit
1 = After power-up, CLRWDT instruction or SLEEP instruction
0 = A WDT time-out occurred

11. • Power on Reset- The task of POR is ensuring that the processor starts at
known address when power is first on, the reset function will set the PC to
starting address.
• Power up timer- A special timer that delay the start of program execution
after the PIC has been reset on power.
• Brown out Reset(BOR)- when the power supply drops below certain
voltage(4v in case of PIC),it causes PIC to reset.
• Watch Dog Timer(WDT)- A simple timer circuit that performs specific
operation after a certain period of time if something goes wrong
• In Circuit Debugger(ICD)- with the ICD we can watch our program run in
the chip/module and find any bugs or programming mistakes as they happen

13. Register Description
ADCON0 - ADC Control Register 0 Control the operation of A/D module
ADCON1 -ADC Control Register 1 Used to configure the GPIO pins for ADC.
Determines the configuration of the PORT A
and PORT E
ADRESH -ADC Result High Register Holds the higher byte of ADC result
ADRESL -ADC Result low Register Holds the lower byte of ADC result
ADC Registers
The A/D module has four 8 bit registers:

14. ADCON0
ADCON0
bit7 6 5 4 3 2 1 bit0
ADCS1 ADCS0 CHS2 CHS1 CHS0 GO/DONE — ADON
• ADCS1 and ADCS2 are used to select A/D Conversion Clock . It should be selected in accordance with device clock.
• CHS2, CHS1 and CHS0 are used to select one of the Analog input channel out of eight channels.
• CHS2-CHS0: Analog Channel Select bits
000 = Channel 0 (AN0/RA0)
001 = Channel 1 (AN1/RA1)
010 = Channel 2 (AN2/RA2)
011 = Channel 3 (AN3/RA3)
100 = Channel 4 (AN4/RA5)
101 = Channel 5 (AN5/RE0)
110 = Channel 6 (AN6/RE1)
111 = Channel 7 (AN7/RE2)
• GO/DONE is the A/D Conversion Status bit. Setting this bit initializes A/D Conversion and will be automatically
cleared when the conversion is complete.
• ADON is used to switch on/off the ADC Module. When it is 1, the ADC Module turns ON and when it is 0, the ADC
Module will be OFF.

15. ADCON1
ADCON1
7 6 5 4 3 2 1 0
ADFM — — — PCFG3 PCFG2 PCFG1 PCFG0
• ADFM - ADC Result Format select bit. Two 8 bit
register (ADRESH and ADRESL) are provided to store the
10-bit result of A/D Conversion. When ADFM is 1, the
result will be right justified, i.e. Most Significant Bits of
ADRESH will be read as 0. When ADFM is 0, the result
will be left justified, i.e. Least Significant Bits of ADRESL
will be read as zero.
• PCFG3 – PCFG0 are the A/D “Port Configuration
Control bits”. Each pin among AN0 – AN7 is configured
as analog , digital or reference voltage inputs according to
the status of these configuration bits as given below.

16. 1. Configure the A/D module:
• Configure analog pins/voltage reference and digital I/O (ADCON1)
• Select A/D input channel (ADCON0)
• Select A/D conversion clock (ADCON0)
• Turn on A/D module (ADON bit of ADCON0)
2. Configure A/D interrupt (if desired):
• Clear ADIF bit
• Set ADIE ,PEIE ,GIE bit
3. Wait the required acquisition time.
4. Start conversion:
• Set GO/DONE bit (ADCON0)
5. Wait for A/D conversion to complete, by either:
• Polling for the GO/DONE bit to be cleared(with interrupts enabled); OR
• Waiting for the A/D interrupt
6. Read A/D result register pair (ADRESH:ADRESL), clear bit ADIF if required.
7. For the next conversion, go to step 1 or step 2, as required.
Steps for A/D conversion

17. A/D conversion timing Diagram

18. Flowchart
Start
Configure ADC module
Set ADC clock
Select Channel
Start Conversion
Display Result
Is
conversion
complete
No
YE
SRead ADC Result

19. #include<16f877.h>
#use delay(clock=20000000)
#use rs232(baud=19200,xmit=pin_c6,rcv=pin_c7)
int adc_data;
void main()
{
setup_adc_ports(ALL_ANALOG);
setup_adc(ADC_CLOCK_INTERNAL);
set_adc_channel(0);
while(1)
{
adc_data = read_adc();
printf("nr ADC %d ",adc_data);
}
}
On-Chip ADC program

20. THANK
YOU