HT86R192 datasheet(15/44 Pages) HOLTEK

15 / 44 page

HT86R192

Rev. 0.00

October 23, 2006

Preliminary

The HT86R192 provides two types of oscillator circuit

for the system clock, i.e., RC oscillator and crystal oscil-

lator. No matter what type of oscillator, the signal is used

for the system clock. The HALT mode stops the system

oscillator and ignores external signal to conserve power.

If the RC oscillator is used, an external resistor between

OSC1 and VSS is required, and the range of the resis-

tance should be from 155k

W to 300kW. The system

clock, divided by 4, is available on OSC2 with pull-high

resistor, which can be used to synchronize external

logic. The RC oscillator provides the most cost effective

solution. However, the frequency of the oscillation may

vary with VDD, temperature, and the chip itself due to

process variations. It is therefore not suitable for timing

sensitive operations where accurate oscillator fre-

quency is desired.

On the other hand, if the crystal oscillator is selected, 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. A resonator

may be connected between OSC1 and OSC2 to replace

the crystal and to get a frequency reference, but two ex-

ternal capacitors in OSC1 and OSC2 are required.

There is another oscillator circuit designed for Timer3

¢s

clock source as the RTC time base which is determined

by OTP option. If the OTP option determines that

Timer3

¢s clock source is from a 32kHz crystal, then a

32kHz crystal should be connected to XIN and XOUT.

Watchdog Timer

- WDT

The WDT clock source is implemented by a dedicated

RC oscillator (WDT oscillator) or instruction clock (sys-

tem clock divided by 4), decided by OTP options. This

timer is designed to prevent a software malfunction or

sequence jumping to an unknown location with unpre-

dictable results. The Watchdog Timer can be disabled

C r y s t a l O s c i l l a t o r

R C O s c i l l a t o r

O S C 1

O S C 2

f S Y S / 4

O S C 1

V D D

R T C O s c i l l a t o r

X O U T

X I N ( P C 6 )

System Oscillator

S y s t e m C l o c k / 4

8 - b i t C o u n t e r

W D T P r e s c a l e r

7 - b i t C o u n t e r

8 - t o - 1 M U X

W D T T i m e - o u t

W S 0 ~ W S 2

M a s k

O p t i o n

S e l e c t

W D T

O S C

Watchdog Timer

Bit No.

Label

Function

EMI

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

EEI

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

ET0I

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

ET1I

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

EIF

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

T0F

Timer 0 request flag (1= active; 0= inactive)

T1F

Timer 1 request flag (1= active; 0= inactive)

Unused bit, read as

²0²

INTC (0BH) Register

Bit No.

Label

Function

ET2I

Controls the Timer 2 interrupt (1= enabled; 0= disabled)

ET3I

Controls the Timer 3 interrupt (1= enabled; 0= disabled)

2~3, 6~7

Unused bit, read as

²0²

T2F

Timer 2 interrupt request flag (1= active; 0= inactive)

T3F

Timer 3 interrupt request flag (1= active; 0= inactive)

INTCH (1EH) 1 Register

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