HT45R4U Datasheet, PDF (31/105 Pages) Holtek Semiconductor Inc – TinyPowerTM A/D Type e-Banking ASSP OTP MCU with LCD

HT45R4U
TinyPower^TM A/D Type
e-Banking ASSP OTP MCU with LCD
Pin-shared Functions
The flexibility of  the microcontroller range  is greatly enhanced by the use of pins that have more
than one function. Limited numbers of pins can force serious design constraints on designers but by
supplying pins with multi-functions, many of these difficulties can be overcome. For some pins, the
chosen function of the multi-function I/O pins is set by configuration options while for others the
function is set by application program control.
External Interrupt Inputs
The external interrupt pins INT0, INT1 are pin-shared with the I/O pins PA2 and PA7 respectively.
For applications not requiring an external interrupt input, the pin-shared external interrupt pin can be
used as a normal I/O pin, however to do this, the external interrupt enable bits in the INTC0 register
must be disabled.
External Timer Clock Input
The external timer pins TMR0, TMR1 and TMR2 are pin-shared with I/O pins. To configure them to
operate as timer inputs, the corresponding control bits in the  timer control register must be correctly
set and the pin must also be setup as an input. Note that the original I/O function will remain even if
the pin is setup to be used as an external timer input.
PFD Output
The device contains a PFD function whose single output is pin-shared with I/O pin PA3. The
output function of this pin is chosen via a configuration option and remains fixed after the device is
programmed. Note that the corresponding bit of the port control register, PAC.3, must setup the pin
as an output to enable the PFD output. If the PAC port control register has setup the pin as an input,
then the pin will function as a normal logic input with the usual pull-high selection, even if the PFD
configuration option has been selected.
A/D Inputs
The device contains a multi-channel A/D converter inputs. All of these analog inputs are pin-
shared with I/O pins. If these pins are to be used as A/D inputs and not as normal I/O pins then the
corresponding bits in the A/D Converter Channel Enable Register, ACER, must be properly set. There
are no configuration options associated with the A/D function. If used as I/O pins, then full pull-high
resistor register remain, however if used as A/D inputs then any pull-high resistor selections associated
with these pins will be automatically disconnected.
Rev. 1.10
31
March 12, 2015