ht82a836r Holtek Semiconductor Inc., ht82a836r Datasheet - Page 55

• Manufacturer Part Number: ht82a836r
• Description: Usb Audio Mcu
• Manufacturer: Holtek Semiconductor Inc.

The START bit in the ADCR register is used to start and
reset the A/D converter. When the microcontroller sets
this bit from low to high and then low again, an analog to
digital conversion cycle will be initiated. When the
START bit is brought from low to high but not low again,
the EOCB bit in the ADCR register will be set to a 1
and the analog to digital converter will be reset. It is the
START bit that is used to control the overall on/off opera-
tion of the internal analog to digital converter.
The EOCB bit in the ADCR register is used to indicate
when the analog to digital conversion process is com-
plete. This bit will be automatically set to 0 by the
microcontroller after a conversion cycle has ended. In
addition, the corresponding A/D interrupt request flag
will be set in the interrupt control register, and if the inter-
rupts are enabled, an appropriate internal interrupt sig-
nal will be generated. This A/D internal interrupt signal
will direct the program flow to the associated A/D inter-
nal interrupt address for processing. If the A/D internal
interrupt is disabled, the microcontroller can be used to
poll the EOCB bit in the ADCR register to check whether
it has been cleared as an alternative method of detect-
ing the end of an A/D conversion cycle.
Rev. 1.00
A/D Converter Clock Source Register
ADCR Register
55
A/D Converter Clock Source Register - ACSR
The clock source for the A/D converter, which originates
from the system clock f
ratio, the value of which is determined by the ADCS1
and ADCS0 bits in the ACSR register.
Although the A/D clock source is determined by the sys-
tem clock f
are some limitations on the maximum A/D clock source
speed that can be selected.
A/D Input Pins
All of the A/D analog input pins are independent analog
inputs and not shared with other I/O pins. Bits
PCR2~PCR0 in the ADCR register, not configuration
options, determine whether the A/D converter is pow-
ered on or powered down. The AVDD4 power supply pin
is used as the A/D converter reference voltage, and as
such analog inputs must not be allowed to exceed this
value. Appropriate measures should also be taken to
ensure that the AVDD4 pin remains as stable and noise
free as possible.
SYS
, and by bits ADCS1 and ADCS0, there
SYS
, is first divided by a division
HT82A836R
March 20, 2008