Datasheet

PIC16C9XX
DS30444E - page 80  1997 Microchip Technology Inc.
FIGURE 12-2: ADCON1 REGISTER (ADDRESS 9Fh)
U-0 U-0 U-0 U-0 U-0 R/W-0 R/W-0 R/W-0
— — — — — PCFG2 PCFG1 PCFG0 R =Readable bit
W = Writable bit
U =Unimplemented
bit, read as ‘0’
- n = Value at POR reset
bit7 bit0
bit 7-3: Unimplemented: Read as '0'
bit 2-0: PCFG2:PCFG0: A/D Port Configuration Control bits
A = Analog input
D = Digital I/O
PCFG2:PCFG0 RA0 RA1 RA2 RA5 RA3 V
REF
000 A A A A A AVDD
001 A A A A VREF RA3
010 A A A A A A
VDD
011 A A A A VREF RA3
100 A A D D A A
VDD
111 D D D D D —
The ADRES register contains the result of the A/D con-
version. When the A/D conversion is complete, the
result is loaded into the ADRES register, the GO/DONE
bit (ADCON0<2>) is cleared, and A/D interrupt flag bit
ADIF is set. The block diagram of the A/D module is
shown in Figure 12-3.
After the A/D module has been configured as desired,
the selected channel must be acquired before the con-
version is started. The analog input channels must
have their corresponding TRIS bits selected as an
input. To determine acquisition time, see Section 12.1.
After this acquisition time has elapsed the A/D conver-
sion can be started. The following steps should be fol-
lowed for doing an A/D conversion:
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 (ADCON0)
2. Configure A/D interrupt (if desired):
• Clear ADIF bit
• Set ADIE bit
• Set 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
OR
• Waiting for the A/D interrupt
6. Read A/D Result register (ADRES), clear bit
ADIF if required.
7. For next conversion, go to step 1 or step 2 as
required. The A/D conversion time per bit is
defined as T
AD. A minimum wait of 2TAD is
required before next acquisition starts.