m37280eksp Mitsumi Electronics, Corp., m37280eksp Datasheet - Page 50

• 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 A-D CONVERTER
12.8.1 A-D Conversion Register (AD)
A-D conversion reigister is a read-only register that stores the result
of an A-D conversion. This register should not be read during A-D
conversion.
12.8.2 A-D Control Register (ADCON)
The A-D control register controls A-D conversion. Bits 2 to 0 of this
register select analog input pins. When these pins are not used as
anlog input pins, they are used as ordinary I/O pins. Bit 3 is the A-D
conversion completion bit, A-D conversion is started by writing “0” to
this bit. The value of this bit remains at “0” during an A-D conversion,
then changes to “1” when the A-D conversion is completed.
Bit 4 controls connection between the resistor ladder and V
not using the A-D converter, the resistor ladder can be cut off from
the internal V
power dissipation.
Fig. 12.8.1 A-D Comparator Block Diagram
50
CC
by setting this bit to “0,” accordingly providing low-
AD1
AD2
AD3
AD4
AD5
AD6
AD7
AD8
A-D control register
(address 00EF
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER with CLOSED CAPTION DECODER
16
Compa-
rator
)
3
b7
M37280MF–XXXSP, M37280MK–XXXSP
CC
. When
A-D control circuit
Data bus
A-D conversion register
Resistor ladder
12.8.3 Comparison Voltage Generator (Resis-
The voltage generator divides the voltage between V
256, and outputs the divided voltages to the comparator as the refer-
ence voltage V
12.8.4 Channel Selector
The channel selector connects an analog input pin, selected by bits
2 to 0 of the A-D control register, to the comparator.
12.8.5 Comparator and Control Circuit
The conversion result of the analog input voltage and the reference
voltage “V
version completion bit and A-D conversion interrupt request bit are
set to “1” at the completion of A-D conversion.
V
Switch tree
SS
8
b0
V
(address 00EE
CC
tor Ladder)
ref
” is stored in the A-D conversion register. The A-D con-
ref
.
and ON-SCREEN DISPLAY CONTROLLER
16
)
MITSUBISHI MICROCOMPUTERS
A-D conversion
interrupt request
M37280EKSP
SS
and V
Rev. 1.0
CC
by