HT86A72 datasheet(25/68 Pages) HOLTEK

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HT86Axx/HT86ARxx

Rev. 1.10

December 12, 2012

selected, then all I/O pins on that port will be connected

to pull-high resistors, individual pins can be selected 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,

PCC, PDC, PEC, etc., to control the input/output config-

uration. 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 asso-

ciated port control register. 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 out-

put. 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.

· A/D Inputs

The device have 4 A/D converter channel inputs. All of

these analog inputs are pin-shared with PC0 to PC3. 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 that 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 selections remain, however if used as A/D in-

puts then any pull-high resistor selections associated

with these pins will be automatically disconnected.

· Serial Interface

The Serial Interface are pin-shared with PD0 to PD3.

If there are to be used as Serial Interface inputs and

not as normal I/O pins then the corresponding bits in

the Serial Interface Control Register that must be

properly set. There are a configuration option associ-

ated with the Serial Interface function. If used as I/O

pins, then full pull-high resistor selections remain,

however if used as the Serial Interface inputs then any

pull-high resistor selections associated with these

pins will be automatically disconnected.

· 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.

Programming Considerations

Within the user program, one of the first things to con-

sider is port initialization. After a reset, all of the I/O data

and port control registers will be set high. This means

that all I/O pins will default to an input state, the level of

which depends on the other connected circuitry and

whether pull-high options have been selected. If the port

control registers, PAC, PBC, PCC, PDC, PEC etc., are

then programmed to setup some pins as outputs, these

output pins will have an initial high output value unless

the associated port data registers, PA, PB, PC, PD, PE,

etc., are first programmed. Selecting which pins are in-

puts and which are outputs can be achieved byte-wide

by loading the correct values into the appropriate port

control register or by programming individual bits in the

port control register using the

²SET [m].i² and ²CLR

[m].i

² instructions. Note that when using these bit control

instructions, a read-modify-write operation takes place.

The microcontroller must first read in the data on the en-

tire port, modify it to the required new bit values and then

rewrite this data back to the output ports.

T 1

T 2

T 3

T 4

T 1

T 2

T 3

T 4

W r i t e t o P o r t

R e a d f r o m P o r t

S y s t e m C l o c k

P o r t D a t a

Read/Write Timing

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