PIC16F871 Microchip Technology Inc., PIC16F871 Datasheet - Page 85

• Manufacturer Part Number: PIC16F871
• Description: 28/40-pin, 8-bit Cmos Flash Microcontrollers
• Manufacturer: Microchip Technology Inc.

10.2
The A/D conversion time per bit is defined as T
A/D conversion requires a minimum 12 T
conversion. The source of the A/D conversion clock is
software selected. The four possible options for T
are:
• 2 T
• 8 T
• 32 T
• Internal A/D module RC oscillator (2-6 s)
TABLE 10-1:
10.3
The ADCON1 and TRIS registers control the operation
of the A/D port pins. The port pins that are desired as
analog inputs must have their corresponding TRIS bits
set (input). If the TRIS bit is cleared (output), the digital
output level (V
The A/D operation is independent of the state of the
CHS2:CHS0 bits and the TRIS bits.
 2003 Microchip Technology Inc.
Note 1:
OSC
OSC
OSC
2:
3:
Selecting the A/D Conversion
Clock
Configuring Analog Port Pins
The RC source has a typical T
When the device frequencies are greater than 1 MHz, the RC A/D conversion clock source is only
recommended for SLEEP operation.
For extended voltage devices (LC), please refer to the Electrical Characteristics (Section 14.1 and 14.2).
Operation
RC
OH
32 T
2 T
8 T
(1, 2, 3)
or V
T
OSC
OSC
OSC
AD
OL
vs. MAXIMUM DEVICE OPERATING FREQUENCIES (STANDARD DEVICES (C))
) will be converted.
AD Clock Source (T
AD
AD
per 10-bit
time of 4 s, but can vary between 2-6 s.
AD
. The
AD
AD
ADCS1:ADCS0
)
00
01
10
11
For correct A/D conversions, the A/D conversion clock
(T
of 1.6 s.
Table 10-1 shows the resultant T
the device operating frequencies and the A/D clock
source selected.
AD
Note 1: When reading the port register, any pin
) must be selected to ensure a minimum T
2: Analog levels on any pin that is defined as
configured as an analog input channel will
read as cleared (a low level). Pins config-
ured as digital inputs will convert an ana-
log input. Analog levels on a digitally
configured input will not affect the
conversion accuracy.
a digital input (including the AN7:AN0
pins), may cause the input buffer to con-
sume current that is out of the device
specifications.
PIC16F870/871
Maximum Device Frequency
1.25 MHz
(Note 1)
20 MHz
AD
5 MHz
Max.
times derived from
DS30569B-page 83
AD
time