PIC18F6621-I/PT Microchip Technology Inc., PIC18F6621-I/PT Datasheet - Page 241

• Manufacturer Part Number: PIC18F6621-I/PT
• Description: 64 PIN, 64 KB FLASH, 3840 RAM, 52 I/O
• Manufacturer: Microchip Technology Inc.

Specifications of PIC18F6621-I/PT

• A/d Inputs: 12-Channel, 10-Bit
• Comparators: 2
• Cpu Speed: 10 MIPS
• Eeprom Memory: 1024 Bytes
• Input Output: 54
• Interface: I2C/SPI/UART/USART
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 64-pin TQFP
• Programmable Memory: 64K Bytes
• Ram Size: 3.8K Bytes
• Speed: 40 MHz
• Timers: 2-8-bit, 3-16-bit
• Voltage, Range: 2-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

20.2
The ADCON2 register allows the user to select an
acquisition time that occurs each time the GO/DONE
bit is set. It also gives users the option to use an
automatically determined acquisition time.
Acquisition time may be set with the ACQT2:ACQT0
bits (ADCON2<5:3>), which provides a range of 2 to
20 T
continues to sample the input for the selected acquisi-
tion time, then automatically begins a conversion.
Since the acquisition time is programmed, there may
be no need to wait for an acquisition time between
selecting a channel and setting the GO/DONE bit.
Automatic
ACQT2:ACQT0 = 000. When the GO/DONE bit is set,
sampling is stopped and a conversion begins. The user
is responsible for ensuring the required acquisition time
has passed between selecting the desired input
channel and setting the GO/DONE bit. This option is
also the default Reset state of the ACQT2:ACQT0 bits
and is compatible with devices that do not offer
programmable acquisition times.
In either case, when the conversion is completed, the
GO/DONE bit is cleared, the ADIF flag is set and the
A/D begins sampling the currently selected channel
again. If an acquisition time is programmed, there is
nothing to indicate if the acquisition time has ended or
if the conversion has begun.
TABLE 20-1:
 2005 Microchip Technology Inc.
AD
. When the GO/DONE bit is set, the A/D module
Selecting and Configuring
Acquisition Time
acquisition
Operation
16 T
32 T
64 T
2 T
4 T
8 T
T
AD
RC
OSC
OSC
OSC
OSC
OSC
OSC
vs. DEVICE OPERATING FREQUENCIES
AD Clock Source (T
is
selected
when
PIC18F6525/6621/8525/8621
AD
)
the
ADCS2:ADCS0
000
100
001
101
010
110
x11
20.3
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. There are seven possible options for T
• 2 T
• 4 T
• 8 T
• 16 T
• 32 T
• 64 T
• Internal RC oscillator
For correct A/D conversions, the A/D conversion clock
(T
of 1.6 µs.
Table 20-1 shows the resultant T
the device operating frequencies and the A/D clock
source selected.
AD
) must be selected to ensure a minimum T
OSC
OSC
OSC
OSC
OSC
OSC
Selecting the A/D Conversion
Clock
Maximum Device Frequency
PIC18F6525/6621/8525/8621
AD
1.25 MHz
2.50 MHz
5.00 MHz
10.0 MHz
20.0 MHz
40.0 MHz
per 10-bit conversion.
AD
—
DS39612B-page 239
times derived from
AD
AD
. The
AD
time
: