HT49C50 datasheet(24/52 Pages) HOLTEK

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HT49C50

August 18, 1999

Label

(TMR1C)

Bits

Function

0~2 Unused bits, read as ²0²

To define the TMR1 active edge of timer/event counter

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

TON

To enable/disable timer counting

(0= disabled; 1= enabled)

TN2

2 to 1 multiplexer control inputs to select the timer/event counter clock source

(0= mask option clock source; 1= system clock/4)

TN1

TN0

To define the operating mode

01= Event count mode (External clock)

10= Timer mode (Internal clock)

11= Pulse Width measurement mode (External clock)

00= Unused

TMR1C register

timer/ event counter. But if the timer/event

counter is turn on, data written to the

timer/event counter is kept only in the

timer/event counter preload register. The

timer/event counter still continues its opera-

tion until an overflow occurs.

When the timer/event counter (reading

TMR0/TMR1) is read, the clock is blocked to

avoid errors. As this may results in a counting

error, blocking of the clock should be taken into

account by the programmer.

It is strongly recommended to load a desired

value into the TMR0/TMR1 register first, then

turn on the related timer/event counter for

proper operation. Because the initial value of

TMR0/TMR1 is unknown.

Due to the timer/event scheme, the program-

mer should pay special attention on the instruc-

tion to enable then disable the timer for the

first time, whenever there is a need to use the

timer/event function, to avoid unpredicatable

result. After this procedure, the timer/event

function can be operated normally. The exam-

ple given below, using two 8-bit width Timer¢s

(timer 0 ;timer 1) cascade into 16-bit width.

START:

mov a, 09h ; Set ET0I&EMI bits to

mov intc0, a ; enable timer 0 and

; global interrupt

mov a, 01h

; Set ET1I bit to enable

mov intc1, a ; timer 1 interrupt

mov a, 80h

; Set operating mode as

mov tmr1c, a ; timer mode and select mask

; option clock source

mov a, 0a0h ; Set operating mode as timer

mov tmr0c, a ; mode and select system

; clock/4

set tmr1c.4 ; Enable then disable timer 1

clr

tmr1c.4 ; for the first time

mov a, 00h

; Load a desired value into

mov tmr0, a ; the TMR0/TMR1 register

mov a, 00h

;

mov tmr1, a ;

set tmr0c.4 ; Normal operating

set tmr1c.4 ;

END

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