HT48R30A-1 Просмотр технического описания (PDF) - Holtek Semiconductor

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HT48R30A-1

I/O Type 8-Bit MCU

Holtek Semiconductor 

HT48R30A-1/HT48C30-1

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 0 interrupt (1= enabled; 0= disabled)

Unused bit, read as ²0²

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

Internal Timer/Event Counter 0 request flag (1= active; 0= inactive)

Unused bit, read as ²0²

Unused bit, read as ²0²

INTC (0BH) Register

Interrupts, occurring in the interval between the rising

edges of two consecutive T2 pulses, will be serviced on

the latter of the two T2 pulses, if the corresponding inter-

rupts are enabled. In the case of simultaneous requests

the following table shows the priority that is applied.

These can be masked by resetting the EMI bit.

No.

Interrupt Source

Priority Vector

a External Interrupt

1

04H

b Timer/Event Counter Overflow 2

08H

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

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

counter interrupt 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 enabling/disabling of interrupts. These bits prevent

the requested 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 op-

tions. No matter what oscillator type is selected, the sig-

nal 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. No other external compo-

nents are required. In stead of a crystal, a resonator 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 (depends

on the options).

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

tor, and no external components are required. Even if

the system enters the power down mode, the system

clock is stopped, but the oscillator still works within a pe-

riod of 65ms at 5V. The WDT oscillator can be disabled

by options to conserve power.

Rev. 2.00

10

April 24, 2009

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