PIC18C242 MICROCHIP [Microchip Technology], PIC18C242 Datasheet - Page 172

• Manufacturer Part Number: PIC18C242
• Description: High-Performance Microcontrollers with 10-Bit A/D
• Manufacturer: MICROCHIP [Microchip Technology]

PIC18CXX2
16.2
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
For correct A/D conversions, the A/D conversion clock
(T
of 1.6 s.
Table 16-1 shows the resultant T
the device operating frequencies and the A/D clock
source selected.
TABLE 16-1:
TABLE 16-2:
DS39026B-page 172
AD Clock Source (T
Operation
2T
4T
8T
16T
32T
64T
RC
Legend: Shaded cells are outside of recommended range.
Note 1: The RC source has a typical T
AD Clock Source (T
Operation
2T
4T
8T
16T
32T
64T
RC
Legend: Shaded cells are outside of recommended range.
Note 1: The RC source has a typical T
AD
OSC
OSC
OSC
OSC
OSC
OSC
) must be selected to ensure a minimum T
OSC
OSC
OSC
OSC
OSC
OSC
• 2T
• 4T
• 8T
• 16T
• 32T
• 64T
• Internal RC oscillator
2: These values violate the minimum required T
3: For faster conversion times, the selection of another clock source is recommended.
4: For device frequencies above 1 MHz, the device must be in SLEEP for the entire conversion or the A/D accuracy may be
2: These values violate the minimum required T
3: For faster conversion times, the selection of another clock source is recommended.
4: For device frequencies above 1 MHz, the device must be in SLEEP for the entire conversion or the A/D accuracy may be
Selecting the A/D Conversion Clock
OSC
OSC
OSC
OSC
OSC
OSC
out of specification.
out of specification.
T
T
AD
AD
AD
AD
ADCS2:ADCS0
ADCS2:ADCS0
)
)
vs. DEVICE OPERATING FREQUENCIES
vs. DEVICE OPERATING FREQUENCIES (FOR EXTENDED, LC, DEVICES)
000
100
001
101
010
110
011
000
100
001
101
010
110
011
AD
per 10-bit conversion.
AD
times derived from
AD
AD
time of 4 s.
time of 6 s.
Device Frequency
20 MHz
100 ns
200 ns
400 ns
800 ns
1.6 s
3.2 s
2 - 6 s
Device Frequency
4 MHz
500 ns
1.0 s
2.0 s
4.0 s
8.0 s
16.0 s
3 - 9 s
AD
(2)
(2)
(2)
AD
are:
(2)
(2)
(2)
(2)
(2)
AD
(1,4)
(1,4)
. The
time
AD
AD
Preliminary
time.
time.
5 MHz
400 ns
800 ns
1.6 s
3.2 s
6.4 s
12.8 s
2 - 6 s
2 MHz
1.0 s
2.0 s
4.0 s
8.0 s
16.0 s
32.0 s
3 - 9 s
16.3
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.
(2)
(2)
(2)
(2)
Note 1: When reading the port register, all pins
Note 2: Analog levels on any pin that is defined as
(1,4)
(1,4)
Configuring Analog Port Pins
configured as analog input channels 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 conver-
sion accuracy.
a digital input (including the AN4:AN0
pins) may cause the input buffer to con-
sume current that is out of the devices
specification.
1.25 MHz
1.6 s
3.2 s
6.4 s
12.8 s
25.6 s
51.2 s
2 - 6 s
1.25 MHz
1.6 s
3.2 s
6.4 s
12.8 s
25.6 s
51.2 s
3 - 9 s
(2)
(2)
(3)
(3)
(3)
(3)
(1,4)
(1,4)
OH
7/99 Microchip Technology Inc.
or V
OL
) will be converted.
6 s
12 s
24 s
48 s
96 s
192 s
2 - 6 s
6 s
12 s
24 s
48 s
96 s
192 s
3 - 9 s
333.33 kHz
333.33 kHz
(3)
(3)
(3)
(3)
(3)
(3)
(3)
(3)
(1)
(1,4)