Holtek HT46R22, Handbook

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In the following tables, D0~D8 or D9 are the A/D conversion data result bits.
Register Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
ADRL D0
¾ ¾ ¾ ¾ ¾ ¾ ¾
ADRH D8 D7 D6 D5 D4 D3 D2 D1
A/D Data Register
-
HT46R47/HT46C47 and HT46R22/HT46C22
Register Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
ADRL D1 D0
¾ ¾ ¾ ¾ ¾ ¾
ADRH D9 D8 D7 D6 D5 D4 D3 D2
A/D Data Register
-
HT46R23/HT46C23 and HT46R24/HT46C24
A/D Converter Control Register
-
ADCR
To control the function and operation of the A/D converter, a control register known as ADCR is pro-
vided. This 8-bit register defines functions such as the selection of which analog channel is con-
nected to the internal A/D converter, which pins are used as analog inputs and which are used as
normal I/Os as well as controlling and monitoring the A/D converter start and reset functions.
One section of this register contains the bits ACS2~ACS0 which define the channel number. As
each of the devices contains only one actual analog to digital converter circuit, each of the individ-
ual 4 or 8 analog inputs must be routed to the converter. It is the function of the ACS2~ACS0 bits in
the ADCR register to determine which analog channel is actually connected to the internal A/D
converter. For the HT46R22/HT46C22, HT46R23/HT46C23 and HT46R24/HT46C24 devices
which have eight analog input channels, the full three bits are required for channel selection, how-
ever, for the HT46R47/HT46C47 devices, which have only four analog input channels, bit ACS2 is
not used and should be kept at a
²
0
²
value. For the HT46R47/HT46C47 devices, if ACS2 is set to
²
1
²
the function of ACS2~ACS0 will be undefined.
The ADCR control register also contains the PCR2~PCR0 bits which determine which pins on
Port B are used as analog inputs for the A/D converter and which pins are to be used as normal
I/Os. For the HT46R22/HT46C22, HT46R23/HT46C23 and HT46R24/HT46C24 devices which
have eight analog input channels, the full three bits are required to fully configure the function of
the bits on Port B. However, for the HT46R47/HT46C47 devices, which have only four analog in-
put channels, if the 3-bit address on PCR2~PCR0 has a value of
²
101
²
or higher, then the same
function as the value
²
100
²
will apply, that is AN0, AN1, AN2 and AN3 will all be set as analog in-
puts. Note that if the PCR2~PCR0 bits are all set to zero, then all the Port B pins will be setup as
normal I/Os and the internal A/D converter circuitry will be powered off to reduce the power con-
sumption.
Chapter 1 Hardware Structure
47