
11
11-2
A-D Converter
32176 Group User’s Manual (Rev.1.01)
11.1 Outline of A-D Converter
The 32176 contains 10-bit resolution A-D Converter of the successive approximation type. The A-D converter has
16 analog input pins (channels) AD0IN0–AD0IN15. In addition to performing conversion individually on each
channel, the A-D Converter can perform conversion successively on all of N channels (N = 1–16) as a single
group. The conversion result can be read out in either 10 or 8 bits.
There are following conversion and operation modes for the A-D conversion:
(1) Conversion Modes
A-D conversion mode
: Ordinary mode in which analog input voltages are converted into digital quantities.
Comparator mode (Note 1) : A mode in which analog input voltage is compared with a preset comparison
voltage to find only the relative magnitude of two quantities. (Useful in only
single operation mode)
(2) Operation Modes
Single mode
: Analog input voltage on one channel is A-D converted once or comparated
(Note 1) with a given quantity.
Scan mode
: Analog input voltages on two or more selected channels (in N channel units, N =
1–16) are sequentially A-D converted.
Single-shot scan mode
: Scan operation is performed for one cycle.
Continuous scan mode
: Scan operation is repeatedly until stopped.
(3) Special Operation Modes
Forcible single mode execution during scan mode : Conversion is forcibly executed in single mode (comparator
mode) during scan operation.
Scan mode start after single mode execution
: Scan operation is started subsequently after executing
conversion in single mode.
Conversion restart
: A-D conversion being executed in single or scan mode is
restarted.
(4) Sample-and-Hold Function
The analog input voltage is sampled when starting A-D conversion, and A-D conversion is performed on the
sampled voltage. This function can be enabled or disabled as necessary.
(5) A-D Disconnection Detection Assist Function
To suppress influences of the analog input voltage leakage from any preceding channel during scan mode
operation, a function is incorporated that helps to fix the electric charge on the chopper amp capacitor to the
given state (AVCC or AVSS) before starting A-D conversion. This function provides a sure and reliable means of
detecting a disconnection in the wiring patterns connecting to the analog input pins.
(6) Inflow Current Bypass Circuit
If an overvoltage or negative voltage is applied to any analog input channel which is currently inactive, a current
flows into or out of the analog input channel currently being A-D converted via the internal circuit, causing the
conversion accuracy to degrade. To solve this problem, the A-D Converter incorporates a circuit that bypasses
such inflow current. This circuit is always enabled.
(7) Conversion Speed
The A-D conversion and comparate speed can be selected from a total of four speeds available: slow mode
(normal or double speed) and fast mode (normal or double speed). The normal speed and double speed in slow
mode are compatible with the 32170 group of Renesas microcomputers.
11.1 Outline of A-D Converter