HD404328 Datasheet, PDF (58/96 Pages) Hitachi Semiconductor – 4 BIT SINGLE CHIP MICROCOMPUTER

HD404328 Series
A/D Converter
The MCU has a built-in A/D converter that uses a sequential comparison method with a resistor ladder. It
can measure four analog inputs with an eight-bit resolution. As shown in the block diagram of figure 34,
the A/D converter has a four-bit A/D mode register, a one-bit A/D start flag, and a four-bit plus four-bit
A/D data register.
AN 0
AN 1
AN 2
AN 3
AV_CC
Internal bus line (S2)
4
1
A/D mode register
(AMR: $016)
A/D start flag
(ADSF: $020)
2
1
1
Internal bus line (S1)
4
4
A/D data register
(ADRL: $017,
ADRU: $018)
IFAD
Comparator
+
–
Control logic
Counter
AV_SS
Operation mode signal
(Stop mode, Watch mode, Subactive mode: Value is 0)
Figure 34 A/D Converter Block Diagram
A/D Mode Register (AMR: $016): Four-bit write-only register which selects the A/D conversion period
and indicates analog input pin information. Bit 0 of the AMR selects the A/D conversion period, and bits 2
and 3 select a channel, as shown in figure 35.
A/D Start Flag (ADSF: $020, Bit 2): One-bit flag that initiates A/D conversion when 1 is written to it.
At the completion of A/D conversion, the converted data is stored in the A/D data register and the ADSF is
cleared. Refer to figure 35.
Note: Use the SEM and SEMD instructions to write data to the ADSF, but make sure that the ADSF is
not written to during A/D conversion.
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