HT86B05 datasheet(33/79 Pages) HOLTEK

33 / 79 page

HT86BXX/HT86BRXX

Rev. 1.60

October 20, 2009

Input/Output Ports

Holtek microcontrollers offer considerable flexibility on

their I/O ports. With the input or output designation of ev-

ery pin fully under user program control, pull-high op-

tions for all ports and wake-up options on certain pins,

the user is provided with an I/O structure to meet the

needs of a wide range of application possibilities.

Depending upon which device or package is chosen,

the microcontroller range provides from 16 to 24

bidirectional input/output lines labeled with port names

PA, PB, PD, etc. These I/O ports are mapped to the Data

Memory with specific addresses as shown in the Special

Purpose Data Memory table. All of these I/O ports can

be used for input and output operations. For input oper-

ation, these ports are non-latching, which means the in-

puts must be ready at the T2 rising edge of instruction

²MOV A,[m]², where m denotes the port address. For

output operation, all the data is latched and remains un-

changed until the output latch is rewritten.

Pull-high Resistors

Many product applications require pull-high resistors for

their switch inputs usually requiring the use of an exter-

nal resistor. To eliminate the need for these external re-

sistors, all I/O pins, when configured as an input have

the capability of being connected to an internal pull-high

resistor. These pull-high resistors are selectable via

configuration options and are implemented using a

weak PMOS transistor. Note that if the pull-high option

is selected, then all I/O pins on that port will be con-

nected to pull-high resistors, individual pins can be se-

lected for pull-high resistor options.

Port A Wake-up

Each device has a HALT instruction enabling the

microcontroller to enter a Power Down Mode and pre-

serve power, a feature that is important for battery and

other low-power applications. Various methods exist to

wake-up the microcontroller, one of which is to change

the logic condition on one of the Port A pins from high to

low. After a

²HALT² instruction forces the microcontroller

into entering a HALT condition, the processor will re-

main idle or in a low-power state until the logic condition

of the selected wake-up pin on Port A changes from high

to low. This function is especially suitable for applica-

tions that can be woken up via external switches. Note

that each pin on Port A can be selected individually to

have this wake-up feature.

I/O Port Control Registers

Each I/O port has its own control register PAC, PBC,

PDC, etc., to control the input/output configuration. With

this control register, each CMOS output or input with or

without pull-high resistor structures can be reconfigured

dynamically under software control. Each pin of the I/O

ports is directly mapped to a bit in its associated port

control register. For the I/O pin to function as an input,

the corresponding bit of the control register must be writ-

ten as a

²1². This will then allow the logic state of the in-

put 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 output register. However, it should be

noted that the program 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.

· Analog Switch

For the HT86B40, HT86B50, HT86B60, HT86BR60,

HT86B70, HT86B80 and HT86B90 devices, pins

PB0~PB7 are pin-shared with analog switch pins K0

to K7. The choice of which function is used is selected

using configuration options and remains fixed after

the device is programmed.

· External RC Oscillator Converter

For the HT86B40, HT86B50, HT86B60, HT86BR60,

HT86B70, HT86B80 and HT86B90 devices, pins

PD4~PD7 are pin-shared with external oscillator con-

verter pins RCOUT, RR, RC and CC. The external RC

oscillator converter function is selected via a configu-

ration option and remains fixed after the device is pro-

grammed.

· I/O Pin Structures

The following diagrams illustrate the I/O pin internal

structures. As the exact logical construction of the I/O

pin may differ from these drawings, they are supplied

as a guide only to assist with the functional under-

standing of the I/O pins. Note also that the specified

pins refer to the largest device package, therefore not

all pins specified will exist on all devices.

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