10-BIT ANALOG TO DIGITAL CONVERTER (ADC)
Table 68. Compare Channels definition
REGISTER DESCRIPTION (Cont’d)
CONTROL LOGIC REGISTER 1 (CLR1)
R252 - Read/Write
Register Page: 63
Reset Value: 0000 1111 (0Fh)
CC[3:0]
Channel A
Channel B
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
3
4
5
6
7
4
5
6
7
8
7
0
SC3 SC2 SC1 SC0 CC3 CC2 CC1 CC0
Bits 7:4 = SC[3:0]: Start Conversion Channel
These four bits define the starting analog input
channel (Autoscan Mode). The first channel ad-
dressed by SC[3:0] is converted, then the channel
number is incremented for the successive conver-
sion, until channel 15 (1111) is converted. When
SC3, SC2, SC1 and SC0 are all set, only channel
15 will be converted.
8
9
9
10
11
12
13
14
15
10
11
12
13
14
Bits 3:0 = CC[3:0]: Compare Channels
The programmed value corresponds to the first of
the two adjacent channels (A) on which it is possi-
ble to define a level window for the converted ana-
log input (see Table 68).
CONTROL LOGIC REGISTER 2 (CLR2)
R253 - Read/Write
Register Page: 63
Reset Value: 1010 0000 (A0h)
Note: If a write access to this register occurs, the
conversion is re-started from the SC[3:0] channel.
7
0
PR2 PR1 PR0 EXTG INTG POW CONT ST
Table 68. Compare Channels definition
CC[3:0]
Channel A
Channel B
Bits 7:5 = PR[2:0]: INTCLK Frequency Prescaler
These bits determine the ratio between the ADC
clock and the system clock (INTCLK) according to
Table 69.
0000
0001
0010
0011
15
0
1
0
1
2
3
2
Table 69. Prescaler programming
T
f
T
f
T
T
f
T
T
Conv
ADC
Sample
ADC
Sample
Conv
ADC
Sample Conv
T
/
A/D clock
(µs)
(MHz)
(µs)
(MHz)
(µs)
(µs)
(MHz)
(µs)
(µs)
PR[2:0]
T
INTCLK
@T
= 8MHz
@T
= 20MHz
@T
=24MHz
INTCLK
INTCLK
INTCLK
000
001
010
011
100
101
110
111
2
4
6
4.00
2.00
1.33
1.00
0.80
0.66
0.57
0.50
2
4
6
8
7
10.00
5.00
3.33
2.50
2.00
1.66
1.43
1.25
Not Allowed
Not Allowed
12.00
6.00
4.00
3.00
2.40
2.00
1.71
1.50
Not Allowed
Not Allowed
14
21
28
2.4
3.2
4
8.4
11.2
14
2
7
8
2.66
9.33
10
12
14
16
Not Allowed
Not Allowed
Not Allowed
Not Allowed
3.33 11.66
14
4.8
5.6
6.4
16.8
19.6
22.4
4
4.66 16.33
5.33 18.66
371/426
9
STMICROELECTRONICS [ ST ]
