HD404339 Datasheet, PDF (59/80 Pages) Hitachi Semiconductor – 4-bit HMCS400-Series microcomputer with large-capacity memory

HD404339 Series
A/D Converter
The MCU also contains a built-in A/D converter that uses a sequential comparison method with a
resistance ladder. It can perform digital conversion of twelve analog inputs with 8-bit resolution. The
following describes the A/D converter.
• A/D mode register 1 (AMR1: $019) is used to select digital or analog ports
• A/D mode register 2 (AMR2: $01A) is used to set the A/D conversion speed and to select digital or
analog ports
• The A/D channel register (ACR: $016) is used to select an analog input channel
• A/D conversion is started by setting the A/D start flag (ADSF: $020, 2) to 1. After the conversion is
completed, converted data is stored in the A/D data register, and at the same time the A/D start flag is
cleared to 0.
• By setting the I_AD off flag (IAOF: $021, 2) to 1, the current flowing through the resistance ladder can be
cut off even while operating in standby or active mode
• The A/D data register is a read-only register consisting of a lower 4 bits and upper 4 bits (ADRL: $017,
ADRU: $018). This register is not cleared by a reset. Data reads during A/D conversion are not
guaranteed. After A/D conversion ends, the resultant 8-bit data is set in this register and held until the
start of the next conversion (figures 51 to 53).
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