m37280eksp Mitsumi Electronics, Corp., m37280eksp Datasheet - Page 52

• Manufacturer Part Number: m37280eksp
• Description: Single-chip 8-bit Cmos Microcomputer With Closed Caption Decoder And On-screen Display Controller
• Manufacturer: Mitsumi Electronics, Corp.

12.8.6 Conversion Method
Note : When the ladder resistor is disconnect from V
Fig. 12.8.3 Changes in A-D Conversion Register and Comparison Voltage during A-D Conversion
52
Set bit 7 of the interrupt input polarity register (address 0212
“1” to generate an interrupt request at completion of A-D conver-
sion.
Set the A-D conversion · INT3 interrupt request bit to “0” (even
when A-D conversion is started, the A-D conversion · INT3 inter-
rupt reguest bit is not set to “0” automatically).
When using A-D conversion interrupt, enable interrupts by setting
A-D conversion · INT3 interrupt request bit to “1” and setting the
interrupt disable flag to “0.”
Set the V
resistor ladder.
Select analog input pins by the analog input selection bit of the A-
D control register.
Set the A-D conversion completion bit to “0.” This write operation
starts the A-D conversion. Do not read the A-D conversion register
during the A-D conversion.
Verify the completion of the conversion by the state (“1”) of the
A-D conversion completion bit, the state (“1”) of A-D conversion ·
INT3 interrupt reguest bit, or the occurrence of an A-D conversion
interrupt.
Read the A-D conversion register to obtain the conversion results.
tion selection bit to “0” between steps
CC
(8th comparison completion)
2nd comparison start
3rd comparison start
8th comparison start
A-D conversion start
1st comparison start
A-D conversion completion
connection selection bit to “1” to connect V
and
Contents of A-D conversion register
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER with CLOSED CAPTION DECODER
1
1 2 3 4 5 6 7 8
1 0 0 0 0 0 0 0
1 2
1 2 3 4 5 6 7
x x x x x
0 0 0 0 0 0 0 0
CC
.
Digital value corresponding to
, set the V
1 0 0 0 0 0 0
x x x x
analog input voltage.
1 0 0 0 0 0
CC
M37280MF–XXXSP, M37280MK–XXXSP
CC
connec-
to the
16
) to
m
: Value determined by mth (m = 1 to 8) result
12.8.7 Internal Operation
When the A-D conversion starts, the following operations are auto-
matically performed.
With the above operations, the analog value is converted into a digi-
tal value. The A-D conversion terminates in a maximum of 50 ma-
chine cycles (12.5 s at f(X
version result is stored in the A-D conversion register.
An A-D conversion interrupt request occurs at the same time as A-D
conversion completion, the A-D conversion · INT3 interrupt request
bit becomes “1.” The A-D conversion completion bit also becomes
“1.”
Table 12.8.1 Expression for V
Note: V
The A-D conversion register is set to “00
The most significant bit of the A-D conversion register becomes
“1, ” and the comparison voltage “V
At this point, V
Bit 7 is determined by the comparison results as follows.
When V
When V
1
A-D conversion register contents “n”
REF
ref
ref
indicates the reference voltage (= Vcc).
< V
> V
V
V
V
V
(decimal notation)
IN
IN
ref
REF
REF
REF
REF
2
2
2
and ON-SCREEN DISPLAY CONTROLLER
2
Reference voltage (V
: bit 7 holds “1”
: bit 7 becomes “0”
is compared with the analog input voltage “V
1 to 255
–
MITSUBISHI MICROCOMPUTERS
0
.......
V
V
V
V
512
IN
REF
REF
REF
REF
4
4
4
) = 8 MHz) after it starts, and the con-
ref
0
–
and V
V
V
V
V
512
256
ref
REF
REF
REF
M37280EKSP
8
REF
8
” is input to the comparator.
REF
ref
16
–
–
)
.”
[V]
V
.....
V
512
512
REF
REF
V
256
REF
Vref (V)
~(n |0.5)
0
Rev. 1.0
IN
.”