PIC12F629/675
TABLE 7-1:
TAD vs. DEVICE OPERATING FREQUENCIES
Device Frequency
5 MHz 4 MHz
A/D Clock Source (TAD)
Operation
2 TOSC
ADCS2:ADCS0
20 MHz
1.25 MHz
±.6 µs
(2)
(2)
(2)
000
100
001
101
010
110
x11
±00 ns
200 ns
400 ns
800 ns
400 ns
800 ns
500 ns
(2)
(2)
(2)
(2)
(2)
4 TOSC
±.0 µs
3.2 µs
8 TOSC
±.6 µs
3.2 µs
6.4 µs
2.0 µs
4.0 µs
6.4 µs
(3)
±6 TOSC
32 TOSC
64 TOSC
A/D RC
±2.8 µs
(3)
(3)
±.6 µs
3.2 µs
8.0 µs
25.6 µs
(3)
(3)
(3)
±2.8 µs
±6.0 µs
5±.2 µs
(1,4)
(1,4)
(1,4)
(1,4)
2 - 6 µs
2 - 6 µs
2 - 6 µs
2 - 6 µs
Legend: Shaded cells are outside of recommended range.
Note 1: The A/D RC source has a typical TAD time of 4 µs 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 ± MHz, the A/D RC clock source is only recommended if the
conversion will be performed during SLEEP.
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.
7.1.5
STARTING A CONVERSION
The A/D conversion is initiated by setting the
GO/DONE bit (ADCON0<±>). When the conversion is
complete, the A/D module:
Note: The GO/DONE bit should not be set in the
same instruction that turns on the A/D.
• Clears the GO/DONE bit
• Sets the ADIF flag (PIR±<6>)
• Generates an interrupt (if enabled).
7.1.6
CONVERSION OUTPUT
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
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.
A/D
conversion
sample.
Instead,
ADRESH:ADRESL registers will retain the value of the
the
FIGURE 7-2:
10-BIT A/D RESULT FORMAT
ADRESH
ADRESL
LSB
(ADFM = 0)
MSB
Bit 7
Bit 0
Bit 7
Bit 0
10-bit A/D Result
Unimplemented: Read as ‘0’
(ADFM = 1)
MSB
LSB
Bit 0
Bit 7
Bit 0
Bit 7
Unimplemented: Read as ‘0
10-bit A/D Result
DS41190C-page 42
2003 Microchip Technology Inc.