Rev. 1.0, 02/00, page 518 of 1141
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 24.3, 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.
24.2.3
A/D Control Register (ADCR)
0
0
1
0
R/W
2
0
R/W
3
0
4
0
R/W
5
0
6
—
—
1
7
R/W
R/W
R/W
HCH1
0
R/W
CK
HCH0
SCH3
SCH2
SCH1
SCH0
Bit :
Initial value :
R/W :
ADCR is a register that sets A/D conversion speed and selects analog input channel. When
executing ADCR setting, make sure that the SST and HST flags in ADCSR is set to 0.
ADCR is an 8-bit readable/writable register that is initialized to H'40 by a reset, and in module
stop mode, standby mode, watch mode, subactive mode and subsleep mode.
Bit 7
Clock Select (CK): Sets A/D conversion speed.
Bit 7
CK
Description
0
Conversion frequency is 266 states
(Initial value)
1
Conversion frequency is 134 states
Note:
A/D conversion starts when 1 is written in SST, or when HST is set to 1. The conversion
period is the time from when this start flag is set until the flag is cleared at the end of
conversion. Actual sample-and-hold takes place (repeatedly) during the conversion
frequency shown in figure 24.2.