
A-D CONVE R T E R
7751 Group User’s Manual
8–6
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
AD
) select bit 1.
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.
b7
b6
b5
b4
b3
b2
b1
b0
A-D control register 1 (Address 1F
16
)
Bit
A-D conversion frequency
(
φ
AD
) select bit 1
4
A-D operation mode select bit 1
(Use in repeat sweep mode 0
and repeat sweep mode 1)
(Note 4)
2
1
0
Bit name
At reset
1
Undefined
RW
Functions
Refer to A-D conversion frequency
(
φ
AD
) select bit 0 (bit 7 at address
1E
16
) ; See
Table 8.2.1
0 : Repeat sweep mode 0
1 : Repeat sweep mode 1
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
7
pin cannot be used as an analog input
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.
3
7 to 5
RW
RW
0
0 0 : AN
0
, AN
1
(2 pins)
0 1 : AN
0
to AN
3
(4 pins)
1 0 : AN
0
to AN
5
(6 pins)
1 1 : AN
0
to AN
7
(8 pins)
(Note 2)
G
Repeat sweep mode 1
(Note 3)
b1 b0
A-D sweep pin select bits
(Valid in single sweep, repeat sweep
mode 0 and repeat sweep mode 1)
(Note 1)
G
Single sweep mode/Repeat sweep
mode 0
b1 b0
0 0 : AN
0
(1 pin)
0 1 : AN
0
, AN
1
(2 pins)
1 0 : AN
0
to AN
2
(3 pins)
1 1 : AN
0
to AN
3
(4 pins)
1
RW
8/10-bit mode select bit
0 : 8-bit mode
1 : 10-bit mode
RW
0
Nothing is assigned.
RW
0
–