Renesas Hitachi H8S/2194 Series Hardware Manual page 605

AHR can be read by the CPU at any time, but the AHR value during A/D conversion is not
fixed. The upper bytes can always be read directly, but the data in the lower bytes is transferred
via a temporary register (TEMP). For details, see section 26.3, Interface to Bus Master.
AHR is a 16-bit read-only register which is initialized to H'0000 at a reset, and in module stop
mode, standby mode, watch mode, subactive mode and subsleep mode.
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