HD404318 Datasheet, PDF (49/66 Pages) Hitachi Semiconductor – 4-bit HMCS400-series microcomputer

HD404318 Series
A/D Converter
The MCU also contains a built-in A/D converter that uses a sequential comparison method with a
resistance ladder. It can perform digital conversion of eight analog inputs with 8-bit resolution. The
following describes the A/D converter.
• A/D mode register 1 (AMR1: $019) is used to select digital or analog ports
• A/D mode register 2 (AMR2: $01A) is used to set the A/D conversion speed and to select digital or
analog ports
• The A/D channel register (ACR: $016) is used to select an analog input channel
• A/D conversion is started by setting the A/D start flag (ADSF: $020, 2) to 1. After the conversion is
completed, converted data is stored in the A/D data register, and at the same time, the A/D start flag is
cleared to 0
• By setting the I_AD off flag (IAOF: $021, 2) to 1, the current flowing through the resistance ladder can be
cut off even while operating in standby or active mode
4
A/D interrupt
request flag
(IFAD)
A/D mode
register 1
(AMR1)
AN₀
AN₁
AN₂
AN₃
AN₄
AN₅
AN₆
AN₇
AV_CC
AV_SS
D/A
3
A/D mode
register 2
(AMR2)
+
Comp
–
Encoder
A/D data
register
(ADRU, L)
A/D
controller
Control signal
for conversion
time
A/D channel
register (ACR)
A/D start flag
(ADSF)
I_AD off flag
(IAOF)
Operating mode signal (1 in stop mode)
Figure 40 A/D Converter Block Diagram
49