48R01A3 데이터 시트보기 (PDF) - Holtek Semiconductor

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48R01A3

Small Package I/O Type 8-Bit OTP MCU

Holtek Semiconductor 

HT48R01A

I/O Port Control Registers

Port A has its own control register, known as PAC, which

controls the input/output configuration. With this control

register, each PA0~PA6 I/O pin with or without pull-high

resistors can be reconfigured dynamically under soft-

ware control. Pins PA0 to PA6 port are 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 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 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 the

I/O pin PA3. To use the pin as an external interrupt in-

put the correct bits in the INTCO register must be pro-

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

setting the appropriate 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 device contains a single Timer/Event Counter.

The Timer/Event Counter has an external input pin,

known as TMR0 which is pin-shared with the I/O pin

PA2. For the shared pin to be used as a Timer/Event

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

figured to be in the Event Counter or Pulse Width

Measurement Mode. This is achieved by setting the

appropriate bits in the Timer/Event Counter Control

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

setting the appropriate bit in the Port Control Register.

Pull-high resistor options can also be selected via the

port pull-high resistor register. Note that even if the pin

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

remains.

· Buzzer

Buzzer output pins BZ and BZ are pin-shared with I/O

pins PA0 and PA1. The buzzer function is selected by

setting the appropriate bits in the CTRL0 register.

Note that the corresponding bits of the port control

register, PAC, must setup the pins as outputs to en-

able the buzzer outputs. If the PAC port control regis-

ter has setup the pins as inputs, then the pins will

functions as normal logic inputs with the usual

pull-high options, even if the buzzer function has been

selected.

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 PA data regis-

ter and PAC 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

PAC port control register, is then programmed to setup

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

tial high output value unless the associated PA port data

register is first programmed. Selecting which pins are in-

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.

S y s te m C lo c k

T1

T2

T3

T4

T1

T2

T3

T4

P o rt D a ta

W r ite to P o r t

R e a d fro m P o rt

Read/Write Timing

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

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

Power Down Mode, various methods are available to

wake the device up. One of these is a high to low transi-

tion of any of the these pins. Single or multiple pins on

Port A can be setup to have this function.

Rev. 1.10

15

August 4, 2008

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