HT46R063B datasheet(39/96 Pages) HOLTEK

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HT46R064B/065B/066B

Rev. 1.00

April 8, 2011

I/O Pin Structures

The 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 understanding of the I/O

pins.

Programming Considerations

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

sider is port initialisation. After a reset, the I/O data reg-

ister and I/O port control register 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, are then programmed to setup

some pins as outputs, these output pins will have an ini-

tial high output value unless the associated port data

puts and which are outputs can be achieved byte-wide

by loading the correct value into the port control register

or by programming individual bits in the port control reg-

ister using the

²SET [m].i² and ²CLR [m].i² 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 entire

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

write this data back to the output ports.

Pins PA0 to PA7 each have a wake-up functions, se-

lected via the PAWK register. When the device is in the

Idle/Sleep Mode, various methods are available to wake

the device up. One of these is a high to low transition of

any of the these pins. Single or multiple pins on Port A

can be setup to have this function.

Timer/Event Counters

The provision of timers form an important part of any

microcontroller, giving the designer a means of carrying

out time related functions. The devices contain from one

to three count-up timer of 8-bit capacity. As the timers

have three different operating modes, they can be con-

figured to operate as a general timer, an external event

counter or as a pulse width capture device. The provi-

sion of an internal prescaler to the clock circuitry on

gives added range to the timers.

There are two types of registers related to the

Timer/Event Counters. The first is the register that con-

tains the actual value of the timer and into which an ini-

tial value can be preloaded. Reading from this register

retrieves the contents of the Timer/Event Counter. The

second type of associated register is the Timer Control

mines how the timer is to be used. The device can have

the timer clock configured to come from the internal

clock source. In addition, the timer clock source can also

be configured to come from an external timer pin.

V D D

W a k e - u p S e l e c t

S y s t e m W a k e - u p

R e a d D a t a R e g i s t e r

C K

C o n t r o l B i t

D a t a B u s

W r i t e C o n t r o l R e g i s t e r

C h i p R e s e t

R e a d C o n t r o l R e g i s t e r

W r i t e D a t a R e g i s t e r

D a t a B i t

I / O p i n

P A o n l y

W e a k

P u l l - u p

P u l l - H i g h

S e l e c t

Generic Input/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 Modify Write Timing

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