HT48C10-1 データシートの表示（PDF） - Holtek Semiconductor

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HT48C10-1

I/O Type 8-Bit MCU

Holtek Semiconductor 

HT48R10A-1/HT48C10-1

Bit No.

0

1

2

3

4

5

6

7

Label

EMI

EEI

ETI

¾

EIF

TF

¾

¾

Function

Controls the master (global) interrupt (1= enabled; 0= disabled)

Controls the external interrupt (1= enabled; 0= disabled)

Controls the timer/event counter interrupt (1= enabled; 0= disabled)

Unused bit, read as ²0²

External interrupt request flag (1= active; 0= inactive)

Internal timer/event counter request flag (1= active; 0= inactive)

Unused bit, read as ²0²

Unused bit, read as ²0²

INTC (0BH) Register

The timer/event counter interrupt request flag (TF), ex-

ternal interrupt request flag (EIF), enable timer/event

counter bit (ETI), enable external interrupt bit (EEI) and

enable master interrupt bit (EMI) constitute an interrupt

control register (INTC) which is located at 0BH in the

data memory. EMI, EEI, ETI are used to control the en-

abling/disabling of interrupts. These bits prevent the re-

quested interrupt from being serviced. Once the

interrupt request flags (TF, EIF) are set, they will remain

in the INTC register until the interrupts are serviced or

cleared by a software instruction.

It is recommended that a program does not use the

²CALL subroutine² within the interrupt subroutine. In-

terrupts often occur in an unpredictable manner or

need to be serviced immediately in some applications.

If only one stack is left and enabling the interrupt is not

well controlled, the original control sequence will be dam-

aged once the ²CALL² operates in the interrupt subrou-

tine.

Oscillator Configuration

There are 3 oscillator circuits in the microcontroller.

V DD

O SC1

470pF

O SC1

O SC2

fS Y S /4

O SC2

N M O S O p e n D r a in

C r y s ta l O s c illa to r

R C O s c illa to r

( In c lu d e 3 2 7 6 8 H z )

System Oscillator

All of them are designed for system clocks, namely the

external RC oscillator, the external Crystal oscillator and

the internal RC oscillator, which are determined by the

options. No matter what oscillator type is selected, the

signal provides the system clock. The HALT mode stops

the system oscillator and ignores an external signal to

conserve power.

If an RC oscillator is used, an external resistor between

OSC1 and VDD is required and the resistance must

range from 24kW to 1MW. The system clock, divided by

4, is available on OSC2, which can be used to synchro-

nize external logic. The RC oscillator provides the most

cost effective solution. However, the frequency of oscil-

lation may vary with VDD, temperatures and the chip it-

self due to process variations. It is, therefore, not

suitable for timing sensitive operations where an accu-

rate oscillator frequency is desired.

If the Crystal oscillator is used, a crystal across OSC1

and OSC2 is needed to provide the feedback and phase

shift required for the oscillator, and no other external

components are required. Instead of a crystal, a resona-

tor can also be connected between OSC1 and OSC2 to

get a frequency reference, but two external capacitors in

OSC1 and OSC2 are required. If the internal RC oscilla-

tor is used, the OSC1 and OSC2 can be selected as

general I/O lines or an 32768Hz crystal oscillator (RTC

OSC). Also, the frequencies of the internal RC oscillator

can be 3.2MHz, 1.6MHz, 800kHz and 400kHz (de-

pended by options).

The WDT oscillator is a free running on-chip RC oscillator,

and no external components are required. Even if the sys-

tem enters the power down mode, the system clock is

stopped, but the WDT oscillator still works with a period of

approximately 65ms@5V. The WDT oscillator can be dis-

abled by options to conserve power.

Watchdog Timer - WDT

The clock source of WDT is implemented by a dedicated

RC oscillator (WDT oscillator), RTC clock or instruction

clock (system clock divided by 4), decided by options.

This timer is designed to prevent a software malfunction

or sequence from jumping to an unknown location with

unpredictable results. The Watchdog Timer can be dis-

abled by an option. If the Watchdog Timer is disabled, all

the executions related to the WDT result in no operation.

The RTC clock is enabled only in the internal RC+RTC

mode.

Rev. 1.90

10

November 4, 2005

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