PIC18F242 MICROCHIP [Microchip Technology], PIC18F242 Datasheet - Page 188

• Manufacturer Part Number: PIC18F242
• Description: 28/40-pin High Performance, Enhanced FLASH Microcontrollers with 10-Bit A/D
• Manufacturer: MICROCHIP [Microchip Technology]

PIC18FXX2
17.2
The A/D conversion time per bit is defined as T
A/D conversion requires 12 T
The source of the A/D conversion clock is software
selectable. The seven possible options for T
• 2 T
• 4 T
• 8 T
• 16 T
• 32 T
• 64 T
• Internal A/D module RC oscillator (2-6 s)
For correct A/D conversions, the A/D conversion clock
(T
of 1.6 s.
Table 17-1 shows the resultant T
the device operating frequencies and the A/D clock
source selected.
TABLE 17-1:
DS39564C-page 186
AD
) must be selected to ensure a minimum T
OSC
OSC
OSC
OSC
OSC
OSC
Selecting the A/D Conversion Clock
Operation
16 T
32 T
64 T
2 T
4 T
8 T
RC
OSC
OSC
OSC
OSC
OSC
OSC
AD Clock Source (T
T
AD
vs. DEVICE OPERATING FREQUENCIES
AD
per 10-bit conversion.
AD
times derived from
ADCS2:ADCS0
AD
)
000
100
001
101
010
110
011
AD
AD
AD
are:
. The
time
17.3
The ADCON1, TRISA and TRISE 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.
Note 1: When reading the port register, all pins con-
PIC18FXX2
10.00 MHz
20.00 MHz
40.00 MHz
1.25 MHz
2.50 MHz
5.00 MHz
Configuring Analog Port Pins
—
2: Analog levels on any pin that is defined as
Maximum Device Frequency
figured as analog input channels will read
as cleared (a low level). Pins configured as
digital inputs will convert an analog input.
Analog levels on a digitally configured input
will not affect the conversion accuracy.
a digital input (including the AN4:AN0
pins) may cause the input buffer to con-
sume current that is out of the device’s
specification.
© 2006 Microchip Technology Inc.
OH
or V
OL
PIC18LFXX2
) will be converted.
10.67 MHz
21.33 MHz
1.33 MHz
2.67 MHz
5.33 MHz
666 kHz
—