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A-D CONVERTER
8.2 Block description
8.2.2 A-D control register 1
Figure 8.2.3 shows the structure of the A-D control register 1.
The A-D operation mode select bit 1 is used to select the operation mode of the A-D converter. The 8/10-
bit mode select bit is used to select the resolution. Refer to Table 8.2.1 for the A-D conversion frequency
(φ
) select bit 1.
AD
b7
b6
b5
b4
b3
b2
Fig. 8.2.3 Structure of A-D control register 1
(1) A-D sweep pin selection bits (bits 1 and 0)
These bits are used to select analog input pins in the single sweep mode, repeat sweep mode 0 and
repeat sweep mode 1. In the single sweep mode and repeat sweep mode 0, pins which are not
selected as analog input pins function as programmable I/O ports.
8–6
b1
b0
A-D control register 1 (Address 1F
Bit
A-D sweep pin select bits
0
(Valid in single sweep, repeat sweep
mode 0 and repeat sweep mode 1)
(Note 1)
1
A-D operation mode select bit 1
2
(Use in repeat sweep mode 0
and repeat sweep mode 1)
(Note 4)
3
8/10-bit mode select bit
A-D conversion frequency
4
(φ
) select bit 1
AD
7 to 5
Nothing is assigned.
Notes 1: These bits are invalid in the one-shot and repeat modes. (They may be either "0" or
"1.")
2: When selecting an external trigger, the AN
pin.
3: Analog input pins which are frequently A-D converted are selected in the repeat
sweep mode 1.
4: Fix this bit to "0" in the one-shot, repeat, and single sweep modes.
5: Writing to each bit of the A-D control register 1 must be performed while the A-D
converter halts.
7751 Group User's Manual
)
16
Bit name
Single sweep mode/Repeat sweep
mode 0
b1 b0
0 0 : AN
0 1 : AN
1 0 : AN
1 1 : AN
Repeat sweep mode 1 (Note 3)
b1 b0
0 0 : AN
0 1 : AN
1 0 : AN
1 1 : AN
0 : Repeat sweep mode 0
1 : Repeat sweep mode 1
0 : 8-bit mode
1 : 10-bit mode
Refer to A-D conversion frequency
(φ
) select bit 0 (bit 7 at address
AD
1E
) ; See Table 8.2.1
16
Functions
At reset
, AN
(2 pins)
0
1
to AN
(4 pins)
0
3
to AN
(6 pins)
0
5
to AN
(8 pins) (Note 2)
0
7
(1 pin)
0
, AN
(2 pins)
0
1
to AN
(3 pins)
0
2
to AN
(4 pins)
0
3
Undefined
pin cannot be used as an analog input
7
RW
1
RW
1
RW
0
RW
0
RW
RW
0
–
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