PIC16F630/676
TABLE 7-1:
TAD vs. DEVICE OPERATING FREQUENCIES
Device Frequency
A/D Clock Source (TAD)
Operation
2 TOSC
ADCS2:ADCS0
20 MHz
100 ns(2)
200 ns(2)
400 ns(2)
800 ns(2)
1.6 μs
5 MHz
4 MHz
500 ns(2)
1.0 μs(2)
2.0 μs
1.25 MHz
1.6 μs
3.2 μs
000
100
001
101
010
110
x11
400 ns(2)
800 ns(2)
1.6 μs
4 TOSC
8 TOSC
6.4 μs
16 TOSC
32 TOSC
64 TOSC
A/D RC
3.2 μs
6.4 μs
4.0 μs
12.8 μs(3)
25.6 μs(3)
51.2 μs(3)
2 - 6 μs(1,4)
8.0 μs(3)
16.0 μs(3)
2 - 6 μs(1,4)
3.2 μs
2 - 6 μs(1,4)
12.8 μs(3)
2 - 6 μs(1,4)
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 1 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<1>). When the conversion is
complete, the A/D module:
Note: The GO/DONE bit should not be set in the
• Clears the GO/DONE bit
same instruction that turns on the A/D.
• Sets the ADIF flag (PIR1<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,
the
ADRESH:ADRESL registers will retain the value of 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
DS40039E-page 44
© 2007 Microchip Technology Inc.
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