HT56RB688_13 datasheet(37/164 Pages) HOLTEK

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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 and INT1 are pin-shared with the I/O pins PA0 and PA1. 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, TMR2 and TMR3 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.

· PWM Outputs

The device contains several PWM outputs name PWM0~PWM3 shared with pins PC4~PC6 and

PA5. The PWM output functions are chosen via registers. Note that the corresponding bit of the port

control register bit must setup the pin as an output to enable the PWM output. If the port control

usual pull-high selection, even if the PWM registers have enabled the PWM function.

· 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 on Port A. 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 Control Register, ADCR, 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.

I/O Pin Structures

The accompanying diagrams illustrate the internal structures of some I/O pin types. As the exact

logical construction of the I/O pin will differ from these drawings, they are supplied as a guide only to

assist with the functional understanding of the I/O pins. The wide range of pin-shared structures does

not permit all types to be shown.

HT56RB688

TinyPowerTM A/D type Smart Card OTP MCU

with LCD, DAC, ISO 7816 and USB Interfaces

Rev. 1.10

April 15, 2013

HT56RB688 Datasheet(PDF) 37 Page - Holtek Semiconductor Inc

HT56RB688 Datasheet(HTML) 37 Page - Holtek Semiconductor Inc

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