PIC16F676-I Datasheet, PDF (46/132 Pages) Microchip Technology – 14-Pin, Flash-Based 8-Bit CMOS Microcontrollers

PIC16F630/676
TABLE 7-1: TAD vs. DEVICE OPERATING FREQUENCIES
A/D Clock Source (TAD)
Device Frequency
Operation ADCS2:ADCS0
20 MHz
5 MHz
4 MHz
1.25 MHz
2 TOSC
000
4 TOSC
100
8 TOSC
001
16 TOSC
101
32 TOSC
010
64 TOSC
110
A/D RC
x11
100 ns⁽²⁾
200 ns⁽²⁾
400 ns⁽²⁾
800 ns⁽²⁾
1.6 s
3.2 s
2 - 6 s^(1,4)
400 ns⁽²⁾
800 ns⁽²⁾
1.6 s
3.2 s
6.4 s
12.8 s⁽³⁾
2 - 6 s^(1,4)
500 ns⁽²⁾
1.0 s⁽²⁾
2.0 s
4.0 s
8.0 s⁽³⁾
16.0 s⁽³⁾
2 - 6 s^(1,4)
1.6 s
3.2 s
6.4 s
12.8 s⁽³⁾
25.6 s⁽³⁾
51.2 s⁽³⁾
2 - 6 s^(1,4)
Legend: Shaded cells are outside of recommended range.
Note 1: The A/D RC source has a typical TAD time of 4 s for VDD > 3.0V.
2: These values violate the minimum required TAD time.
3: For faster conversion times, the selection of another clock source is recommended.
4: When the device frequency is greater than 1 MHz, the A/D RC clock source is only recommended if the
conversion will be performed during Sleep.
7.1.5 STARTING A CONVERSION
The A/D conversion is initiated by setting the
GO/DONE bit (ADCON0<1>). When the conversion is
complete, the A/D module:
• Clears the GO/DONE bit
• Sets the ADIF flag (PIR1<6>)
• Generates an interrupt (if enabled)
If the conversion must be aborted, the GO/DONE bit
can be cleared in software. The ADRESH:ADRESL
registers will not be updated with the partially complete
A/D conversion sample. Instead, the
ADRESH:ADRESL registers will retain the value of the
previous conversion. After an aborted conversion, a
2 TAD delay is required before another acquisition can
be initiated. Following the delay, an input acquisition is
automatically started on the selected channel.
Note: The GO/DONE bit should not be set in the
same instruction that turns on the A/D.
7.1.6 CONVERSION OUTPUT
The A/D conversion can be supplied in two formats: left
or right shifted. The ADFM bit (ADCON0<7>) controls
the output format. Figure 7-2 shows the output formats.
FIGURE 7-2:
10-BIT A/D RESULT FORMAT
ADRESH
ADRESL
(ADFM = 0)
MSB
bit 7
LSB
bit 0
bit 7
bit 0
(ADFM = 1)
bit 7
10-bit A/D Result
MSB
bit 0
bit 7
Unimplemented: Read as ‘0’
LSB
bit 0
Unimplemented: Read as ‘0’
10-bit A/D Result
DS40039F-page 46
 2010 Microchip Technology Inc.