Renesas M32R/ECU Series, User Manual

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11
11-2
A-D Converters
32180 Group User's Manual (Rev.1.0)
11.1 Outline of A-D Converters
The 32180 contains two 10-bit A-D Converters of the successive approximation type (A-D0 and A-D1 Converters).
Each A-D Converter has 16 input channels. 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 machine 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 wrapping around 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 Mitsubishi microcomputers.
11.1 Outline of A-D Converters