The document discusses the analog to digital converter (ADC) functionality of the PIC16F877A microcontroller. It has 8 analog input channels, with 5 on PORTA and 3 on PORTE. It has a 10-bit resolution. The basic registers used for ADC conversion are ADCON0 and ADCON1. ADCON0 controls ADC operation and channel selection. ADCON1 configures port pin functions.

1. ADC
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2. • PIC16F877A has 8 analog input channels
• 5 Channels on PORT A
• 3 Channels on PORT E
•10 bit resolution
• Basic registers used for ADC conversion
• ADCON0
• ADCON1
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3. ADCON0
• Controls the operation of A/D module
Bit 7 Bit 0
ADCS1 ADCS2 CHS2 CHS1 CHS0 ADGO ---- ADON
Bit 7:6 – ADCS1:ADCS2 – A/D conversion clock select bit
Bit 5:3 – CHS2:CHS0 – Analog channel select bit
Bit 2 – ADGO – A/D conversion status bit
Bit 1 – Unimplemented – Set as ‘0’
Bit 0 – ADON – A/D ON bit
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4. ADCS1 ADCS2 CLOCK
0 0 Fosc/2
0 1 Fosc/8
1 0 Fosc/32
1 1 FRC(Clock derived from Internal A/D RC Oscillator)
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5. CHS2 CHS1 CHS0 Analog Channel
0 0 0 Channel 0,(AN0)
0 0 1 Channel 1,(AN1)
0 1 0 Channel 2,(AN2)
0 1 1 Channel 3,(AN3)
1 0 0 Channel 4,(AN4)
1 0 1 Channel 5,(AN5)
1 1 0 Channel 6,(AN6)
1 1 1 Channel 7,(AN7)
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6. ADGO:
When ADON=1
1 = Starts A/D conversion(automatically cleared by
hardware when conversion is complete)
0 = A/D not in progress
ADON:
1 = A/D conversion module is powered up
0 = A/D conversion is shut off
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7. ADCON1
• Configure the functions of port pins
Bit 7 Bit 0
------- -------- ADFM ------ PCFG3 PCFG2 PCFG1 PCFG0
Bit 7:6 – Unimplemented – Read as ‘0’
Bit 5 – ADFM – A/D result format select
Bit 4 – Unimplemented – Read as ‘0’
Bit 3:0 – PCFG3:PCFG0 – A/D port configuration control bits
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8. ADFM :
1 = Right justified. 6 MSB of ADRESH are read as ‘0’
0 = Left justified. 6 LSB of ADRESL are read as ‘0’
10- Bit Result
ADFM=1 ADFM=0
7 210 7 0 7 0 7 65 0
0000 00 RESULT RESULT 0 0 0000
ADRESH ADRESL ADRESH ADRESL
10-bit 10-bit
Right justified Left justified
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9. PCFG3:0 AN7 AN6 AN5 AN4 AN3 AN2 AN1 AN0
0000 A A A A A A A A
0001 A A A A VREF+ A A A
0010 D D D A A A A A
0011 D D D A VREF+ A A A
0100 D D D D A D A A
0101 D D D D VREF+ D A A
011X D D D D D D D D
1000 A A A A VREF+ VREF- A A
1001 D D A A A A A A
1010 D D A A VREF+ A A A
1011 D D A A VREF+ VREF- A A
1100 D D D A VREF+ VREF- A A
1101 D D D D VREF+ VREF- A A
1110 D D D D D D D A
1111 D D D D VREF+ VREF- D A
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