D-A CONVERTER
7902 Group User’s Manual
14-3
14.2 Block description
14.2.1 D-A control register
Figure 14.2.2 shows the structure of the D-A control register.
Pin DAi (i = 0 to 2) serves as the analog voltage output pin of the D-A converter. Since pin DAi is equipped
with no internal buffer amplifier, it is necessary to connect a buffer amplifier externally to pin DA i, if this
pin is needed to be connected with a low-impedance load.
Pin DAi is multiplexed with an analog input, serial I/O, or external interrupt input pin. When any of the
D-Ai output enable bits is set to “1” (output enabled), the corresponding pin is used only as pin DAi, not
as any other multiplexed input/output pin (including programmable I/O port pin).
Fig. 14.2.2 Structure of D-A control register
(1) D-Ai output enable bits (Bits 0 to 2)
Setting any of the D-Ai output enable bits to “1” (output enabled) allows the corresponding pin DAi to
output D-A converted analog voltage, regardless of the contents of the corresponding bits of the port
P7 and P8 registers.
14.2.2 D-A Register i (i = 0 to 2)
Each pin DAi outputs the analog voltage corresponding to the value loaded in the D-A register i. Figure
14.2.3 shows the structure of the D-A register i.
0
1
2
7 to 3
Bit name
Bit
Function
At reset
R/W
D-A0 output enable bit
D-A1 output enable bit
D-A2 output enable bit
Nothing is assigned.
b7 b6 b5 b4 b3 b2 b1 b0
0: Output is disabled.
1: Output is enabled. (Notes 1, 2)
0: Output is disabled.
1: Output is enabled. (Notes 1, 2)
0: Output is disabled.
1: Output is enabled. (Notes 1, 2)
0
RW
—
D-A control register (Address 9616)
Notes 1: Pin DAi is multiplexed with analog input pin, serial I/O pin, and external interrupt input pin. When a D-Ai output enable bit =
“1” (in other words, output is enabled.), however, the corresponding pin cannot function as any other multiplexed input/
output pin (including programmable I/O port pin).
2: When not using the D-A converter, be sure to clear the contents of this bit to “0.”
0
7 to 0
Bit
D-A register i (i = 0 to 2) (Addresses 9816 to 9A16)
Function
At reset
R/W
Any value from 0016 through FF16 can be set (Note), and this value is D-A
converted and is output.
RW
b0
b7
Fig. 14.2.3 Structure of the D-A register i
Undefined
Note: When not using the D-A converter, be sure to clear the contents of these bits to “0016.”