HT36M4 datasheet(13/23 Pages) HOLTEK

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HT36M4

Rev. 1.00

August 15, 2005

RESET Conditions

RES reset during power-up

RES reset during normal operation

RES wake-up HALT

WDT time-out during normal operation

WDT wake-up HALT

Note:

²u² stands for ²unchanged²

To guarantee that the system oscillator has started and

stabilized, the SST (System Start-up Timer) provides an

extra-delay of 1024 system clock pulses during system

power up or when the system awakes from a HALT

state.

When a system power-up occurs, the SST delay is

added during the reset period. But when the reset co-

mes from the RES pin, the SST delay is disabled. Any

wake-up from HALT will enable the SST delay.

The functional units chip reset status are shown below.

Program Counter

000H

Interrupt

Disable

Prescaler

Clear

WDT

Clear. After master reset,

WDT begins counting

Timer/Event Counter (0/1) Off

Input/output ports

Input mode

Stack Pointer

Points to the top of the

stack

Timer/Event Counter

Two timer/event counters are implemented in the

HT36M4. The Timer/Event Counter 0 and Timer/Event

Counter 1 contain 16-bit programmable count-up coun-

ters and the clock comes from the system clock divided

by 4.

There are three registers related to Timer/Event Coun-

ter 0; TMR0H (0CH), TMR0L (0DH), TMR0C (0EH).

Writing TMR0L only writes the data into a low byte

buffer, and writing TMR0H will write the data and the

contents of the low byte buffer into the Timer/Event

Counter 0 preload register (16-bit) simultaneously. The

Timer/Event Counter 0 Preload register is changed by

writing TMR0H operations and writing TMR0L will keep

the Timer/Event Counter 0 Preload register unchanged.

Reading TMR0H will also latch the TMR0L into the low

byte buffer to avoid a false timing problem. Reading

TMR0L returns the contents of the low byte buffer. In

other words, the low byte of the Timer/Event Counter 0

cannot be read directly. It must read the TMR0H first to

make the low byte contents of the Timer/Event Counter

0 latched into the buffer.

There are three registers related to the Timer/Event

Counter 1; TMR1H (0FH), TMR1L (10H), TMR1C (11H).

The Timer/Event Counter 1 operates in the same man-

ner as Timer/Event Counter 0.

The TMR0C is the Timer/Event Counter 0 control regis-

ter, which defines the Timer/Event Counter 0 options.

The Timer/Event Counter 1 has the same options with

Timer/Event Counter 0 and is defined by TMR1C.

The Timer/Event Counter control registers define the

operating mode, counting enable or disable and active

edge.

The TM0, TM1 bits define the operating mode. The

Event count mode is used to count external events,

which means the clock source comes from an external

(TMR) pin. The Timer mode functions as a normal timer

with the clock source coming from the instruction clock.

The pulse width measurement mode can be used to

count the high or low level duration of the external signal

(TMR). The counting is based on the instruction clock.

In the Event count or Timer mode, once the timer/event

counter starts counting, it will count from the current

contents in the timer/event counter to FFFFH. Once

overflow occurs, the counter is reloaded from the

Timer/Event Counter Preload register and simulta-

neously generates the corresponding interrupt request

flag (T0F/T1F; bit 5/6 of INTC).

Bit No.

Label

Function

0~2

Unused bit, read as

²0²

3TE

Defines the TMR active edge of the Timer/Event Counter 0

(0=active on low to high; 1=active on high to low)

TON

Enable/disable timer counting (0=disable; 1=enable)

Unused bit, read as

²0²

TM0

TM1

Defines the operating mode

01=Event count mode (External clock)

10=Timer mode (Internal clock)

11=Pulse width measurement mode

00=Unused

TMR0C/TMR1C (0EH/11H) Register

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