M16C65 Datasheet, PDF (699/829 Pages) Renesas Technology Corp – RENESAS MCU M16C FAMILY / M16C/60

Under development
M16C/65 Group
Preliminary Specification
This is a preliminary specification and is subject to change.
27. A/D Converter
27.3.3 A/D Conversion Result
When reading the ADi register before A/D conversion is completed, the undefined value is read. Read
the ADi register after completing A/D conversion. Use the following procedure to detect the completion
of A/D conversion.
• In one-shot mode and single sweep mode:
The IR bit in the ADIC register becomes 1 (interrupt requested) at the completion of A/D
conversion. Ensure that the IR bit becomes 1 to read the ADi register.
when not using A/D interrupt, set the IR bit to 0 (interrupt not requested) by a program after reading
the ADi register.
• In repeat mode, repeat sweep mode 0, and repeat sweep mode 1:
The IR bit remain unchanged (no interrupt request is generated). At first, read the ADi register after
one A/D conversion period elapses (refer to 27.3.1 “A/D Conversion Cycle”). After that, whenever
the ADi register is read, the conversion result which has been obtained before reading is read.
The ADi register is overwritten in every A/D conversion. Read the value before the ADi register is
overwritten.
27.3.4 Extended Analog Input Pins
In one-shot mode and repeat modes, pins ANEX0 and ANEX1 can be used as analog input pins by
setting bits ADEX1 to ADEX0 in the ADCON1 register.
The A/D conversion result of pins ANEX0 and ANEX1 are respectively stored in registers AD0 and
AD1.
27.3.5 Current Consumption Reduce Function
When the A/D converter is not in use, the power consumption can be reduced by setting the ADSTBY
bit in the ADCON1 register to 0 (A/D operation stopped: standby) to shut off any analog circuit current
flow.
To use the A/D converter, set the ADSTBY bit to 1 (A/D operation enabled) and wait for 1 φAD cycle or
more before setting the ADST bit in the ADCON0 register to 1 (A/D conversion start). Do not set bits
ADST and ADSTBY to 1 at the same time.
Also, do not set the ADSTBY bit to 0 (A/D operation stopped: standby) during A/D conversion.
27.3.6 Open-Circuit Detection Assist Function
The A/D converter has a function to set charge of the sampling capacitor to a predefined state (AVCC
or AVSS) before A/D conversion starts in order to prevent the effect of analog input voltage of previous
conversion. This function enables to detect open-circuit of a trace connected to the analog input pin
certainly.
Figure 27.5 shows A/D Open-Circuit Detection Example on AVCC (Precharge) and Figure 27.6 shows
A/D Open-Circuit Detection Example on AVSS (Predischarge).
The conversion result in open-circuit depends on the external circuit. Use this function only after careful
evaluation for the system.
REJ09B0484-0030 Rev.0.30 Sep 09, 2008
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