HT56R26 View Datasheet(PDF) - Holtek Semiconductor
Part Name
Description
MFG CO.
'HT56R26' PDF : 134 Pages View PDF
HT56R22/HT56R23/HT56R24/HT56R25/HT56R26
I/O Port Control Registers
Each Port has its own control register, known as PAC,
PBC, PCC, PDC, PEC, PFC and PGC which controls
the input/output configuration. With this control register,
each I/O pin with or without pull-high resistors can be re-
configured dynamically under software control. For the
I/O pin to function as an input, the corresponding bit of
the control register must be written as a ²1². This will
then allow the logic state of the input pin to be directly
read by instructions. When the corresponding bit of the
control register is written as a ²0², the I/O pin will be
setup as a CMOS output. If the pin is currently setup as
an output, instructions can still be used to read the out-
put register. However, it should be noted that the pro-
gram will in fact only read the status of the output data
latch and not the actual logic status of the output pin.
Pin-shared Functions
The flexibility of the microcontroller range is greatly en-
hanced by the use of pins that have more than one func-
tion. Limited numbers of pins can force serious design
constraints on designers but by supplying pins with
multi-functions, many of these difficulties can be over-
come. 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 pro-
gram control.
· External Interrupt Input
The external interrupt pin, INT0/INT1, are pin-shared
with an I/O pins. To use the pins as external interrupt
inputs the correct bits in the INTC0 register must be
programmed. The pin must also be setup as an input
by setting bit in the Port Control Register. A pull-high
resistor can also be selected via the appropriate port
pull-high resistor register. Note that even if the pin is
setup as an external interrupt input the I/O function
still remains.
· External Timer/Event Counter Input
The Timer/Event Counter pins, TC0, TC1, TC2 and
TC3 are pin-shared with I/O pins. For these shared
pins to be used as Timer/Event Counter inputs, the
Timer/Event Counter must be configured to be in the
Event Counter or Pulse Width Capture Mode. This is
achieved by setting the appropriate bits in the
Timer/Event Counter Control Register. The pins must
also be setup as inputs by setting the appropriate bit
in the Port Control Register. Pull-high resistor options
can also be selected using the port pull-high resistor
registers. Note that even if the pin is setup as an exter-
nal timer input the I/O function still remains.
· PFD Output
The PFD function output is pin-shared with an I/O pin.
The output function of this pin is chosen using the
Configuration option. Note that the corresponding bit
of the port control register, must setup the pin as an
output to enable the PFD output. If the 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 function has been
selected.
· PWM Outputs
The PWM function whose outputs are pin-shared with
I/O pins. The PWM output functions are chosen using
the PWMnL and PWMnH (n=0~3) registers. Note that
the corresponding bit of the port control registers, for
the output pin, must setup the pin as an output to en-
able the PWM output. If the pins are setup as inputs,
then the pin will function as a normal logic input with
the usual pull-high selections, even if the PWM regis-
ters have enabled the PWM function.
· SCOM Driver Pins
Pins PB0~PB3 on Port B can be used as LCD COM
driver pins. This function is controlled using the
SCOMC register which will generate the necessary
1/2 bias signals on these four pins.
· A/D Inputs
Each device in this series has eight inputs to the A/D
converter. 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 I/O pins then the corresponding PCRn bits
in the A/D converter control register, ADPCR, must be
properly setup. There are no configuration options as-
sociated with the A/D converter. If chosen as I/O pins,
then full pull-high resistor configuration options re-
main, however if used as A/D inputs then any pull-high
resistor configuration options associated with these
pins will be automatically disconnected.
Pin Remapping Configuration
The pin remapping function enables the function pins
INT0/1, TC0/1, PFD, PWM0/1/2 to be located on differ-
ent port pins. It is important not to confuse the Pin Re-
mapping function with the Pin-shared function, these
two functions have no interdependence.
The PMAP0~7 bit in the PINMAP register allows the
three function pins INT0/1, TC0/1, PFD, PWM0/1/2 to
be remapped to different port pins. After power up,
these bits will be reset to zero, which will define the de-
fault port pins to which these three functions will be
mapped. Changing this bit will move the functions to
other port pins.
Examination of the pin names on the package diagrams
will reveal that some pin function names are repeated,
this indicates a function pin that can be remapped to
other port pins. If the pin name is bracketed then this in-
dicates its alternative location. Pin names without brack-
ets indicates its default location which is the condition
after Power-on.
Rev. 1.30
44
December 26, 2014
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