RX610 Group
24. D/A Converter
R01UH0032EJ0120 Rev.1.20
Page 815 of 1006
Feb 20, 2013
24.4
Usage Notes
24.4.1
Module Stop Function Setting
Operation of the D/A converter can be disabled or enabled by using the module stop control register. The initial setting is
for operation of the D/A converter to be halted. Register access is enabled by clearing the module stop state. For details,
refer to section 8, Low Power Consumption.
24.4.2
Operation of the D/A Converter in Module Stop State
When this LSI enters the module stop state with D/A conversion enabled, the D/A outputs are retained, and the analog
power supply current is the same as during D/A conversion. If the analog power supply current has to be reduced in the
module stop state, disable D/A conversion by clearing the DAOE1, DAOE0, and DAE bits to 0.
24.4.3
Operation of the D/A Converter in Software Standby Mode
When this LSI enters software standby mode with D/A conversion enabled, the D/A outputs are retained, and the analog
power supply current is the same as during D/A conversion. If the analog power supply current has to be reduced in
software standby mode, disable D/A conversion by clearing the DAOE1, DAOE0, and DAE bits to 0.
24.4.4
Note on Entering Deep Software Standby Mode
When this LSI enters deep software standby mode with D/A conversion enabled, the outputs of the D/A converter are
placed in a high impedance state.
24.4.5
Note when Using the A/D Converter and D/A Converter Simultaneously
Because the A/D converter and the D/A converter of the RX610 Group use the same power supply, conversion accuracy
of A/D conversion result may get affected depending on the usage. The conversion accuracy is likely to be affected in the
following cases.
•
If the D/A data register (DADR) of D/A converter is rewritten while the A/D converter is being operated
•
If the D/A control register (DACR) is rewritten by setting a value other than 000h to the DADR
When conversion accuracy is affected, implement the following measures.
(1) Method of rewriting DADR with AD converter operated
When rewriting the DADR while the AD converter is being operated, implement any one of the following methods.
1
When the DADR register is rewritten, discard the result of the A/D converter that is undergoing conversion.
2
When the DADR register is written, perform an averaging procedure for the A/D conversion result using a program.
Averaging procedure example: Perform A/D conversion of the analog input to identical pins successively for four
times.
3
Calculate an average of two values of the A/D conversion result excluding the maximum and minimum values.
4
Set the rewriting procedure for DADR register as follows.
5
When the DADR register is written, keep the difference before changing and after changing at less than 100h, and
when the next data is written, keep an interval of more than one conversion period of A/D converter. However, when
rewriting is performed by maintaining the difference before and after changing at less than 080h, it is not necessary
to maintain an interval of more than one conversion period of A/D converter.