ht82j30r Holtek Semiconductor Inc., ht82j30r Datasheet - Page 32

• Manufacturer Part Number: ht82j30r
• Description: Ht82j30r/ht82j30a -- 16 Channel A/d Mcu With Spi Interface
• Manufacturer: Holtek Semiconductor Inc.

should not be set to 00 . Doing so will give A/D clock peri-
ods that are less than the minimum A/D clock period which
may result in inaccurate A/D conversion values. Refer to
the following table for examples, where values marked
with an asterisk * show where, depending upon the de-
vice, special care must be taken, as the values may be
less than the specified minimum A/D Clock Period.
A/D Input Pins
All of the A/D analog input pins are pin-shared with the
I/O pins on Port B and Port C. Bits PCR3~PCR0 in the
ACSR register, not configuration options, determine
whether the input pins are setup as normal Port B and
Port C input/output pins or whether they are setup as an-
alog inputs. In this way, pins can be changed under pro-
gram control to change their function from normal I/O
operation to analog inputs and vice versa. Pull-high resis-
tors, which are setup through configuration options, apply
to the input pins only when they are used as normal I/O
Rev. 1.10
12MHz
1MHz
2MHz
4MHz
8MHz
f
SYS
ADCS1, ADCS0=00
(f
500ns*
250ns*
167ns*
SYS
2 s
1 s
/2)
A/D Converter Clock Source Register
ADCS1, ADCS0=01
A/D Clock Period Examples
(f
667ns*
SYS
8 s
4 s
2 s
1 s
A/D Clock Period (t
/8)
32
pins, if setup as A/D inputs the pull-high resistors will be
automatically disconnected. Note that it is not necessary
to first setup the A/D pin as an input in the PBC or PCC
port control register to enable the A/D input as when the
PCR3~PCR0 bits enable an A/D input, the status of the
port control register will be overridden. The VREF pin is
used as the A/D converter reference voltage. The value
of VREF must not exceed the VDD value. Appropriate
measures should also be taken to ensure that the VREF
pin remains as stable and noise free as possible. Note
that on the 28-pin package, there is no VREF pin as it is
internally connected to VDD.
Initialising the A/D Converter
The internal A/D converter must be initialised in a spe-
cial way. Each time the Port B and Port C A/D channel
selection bits are modified by the program, the A/D con-
verter must be re-initialised. If the A/D converter is not
initialised after the channel selection bits are changed,
ADCS1, ADCS0=10
Undefined
Undefined
Undefined
Undefined
Undefined
AD
)
HT82J30R/HT82J30A
ADCS1, ADCS0=11
Undefined
Undefined
Undefined
Undefined
Undefined
March 13, 2008