HT48R005 datasheet(29/62 Pages) HOLTEK

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HT48R005/HT46R005

Rev. 1.00

November 29, 2011

I/O Port Control Registers

Each Port has its own control register, known as PAC

which controls the input/output configuration. With this

control register, each I/O pin with or without pull-high re-

sistors can be reconfigured dynamically under software

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

sponding 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 correspond-

ing 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.

· External Interrupt Input

The external interrupt pin, INT, is pin-shared with an

I/O pin. To use the pin as an external interrupt input

the correct bits in the INTC0 register must be pro-

grammed. The pin must also be setup as an input by

setting PAC2 bit in the Port Control Register. A

pull-high resistor can also be selected via the appro-

priate 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 pin, TMR is pin-shared with

I/O pin. For this shared pin to be used as Timer/Event

Counter input, the Timer/Event Counter must be con-

figured to be in the Event Counter or Pulse Width Cap-

ture 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 ap-

propriate bit in the Port Control Register. Pull-high re-

sistor options can also be selected using the port

pull-high resistor registers. Note that even if the pin is

setup as an external timer input the I/O function still re-

mains.

· Buzzer Output

The device contains a Buzzer function whose single

or dual outputs are pin-shared with I/O pins. The out-

put function of these pin are chosen using the CTRL0

control register, must setup the pin as an output to en-

able the BZ, BZ output. If the port control register has

setup these pins as input, then these pins will function

as normal logic input with the usual pull-high selec-

tion, even if the Buzzer function has been selected.

· A/D Inputs

Each device in this series has either four or eight in-

puts to the A/D converter. 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 I/O pins then

the corresponding PCRn bits in the A/D converter

control register, ADCR, must be properly setup. There

are no configuration options associated with the A/D

converter. If chosen as I/O pins, then full pull-high re-

sistor configuration options remain, however if used

as A/D inputs then any pull-high resistor configuration

options associated with these pins will be automati-

cally disconnected.

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

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.

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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