HT48R50A datasheet(20/46 Pages) HOLTEK

20 / 46 page

HT48R50A-1

Rev. 1.10

July 2, 2001

0. The internal clock source can be selected as

coming from (can always be optioned) or fRTC

(enabled only system oscillator in the Int.

RC+RTC mode) by ROM code option. The exter-

nal clock input allows the user to count external

events, measure time intervals or pulse widths,

or to generate an accurate time base and PFD

signals.

Using the internal clock sources, there are 2

reference time-bases for Timer/Event Counter

1. The internal clock source can be selected as

coming from fSYS/4 (can always be optioned) or

fRTC (enable only the system oscillator in the

Int. RC+RTC mode) by ROM code option. The

external clock input allows the user to count ex-

ternal events, measure time intervals or pulse

widths or to generate an accurate time base.

There are 2 registers related to the Timer/Event

Counter 0; TMR0 ([0DH]), TMR0C ([0EH]). Two

physical registers are mapped to TMR0 location;

writing TMR0 makes the starting value be placed

intheTimer/EventCounter0preloadregisterand

reading TMR0 gets the contents of the

Timer/Event Counter 0. The TMR0C is a

timer/event counter control register, which de-

finessomeoptions.

There are 3 registers related to Timer/Event

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

TMR1C (11H). Writing TMR1L will only put

the written data to an internal lower-order byte

buffer (8 bits) and writing TMR1H will transfer

the specified data and the contents of the

lower-order byte buffer to TMR1H and TMR1L

preload registers, respectively. The

Timer/Event Counter 1 preload register is

changed by each writing TMR1H operations.

Reading TMR1H will latch the contents of

TMR1H and TMR1L counters to the destina-

tion and the lower-order byte buffer, respec-

tively. Reading the TMR1L will read the

contents of the lower-order byte buffer. The

TMR1C is the Timer/Event Counter 1 control

TM 1

TM 0

TM R 0

TM 1

TM 0

TO N

P u l s e W i dt h

M eas ur e m ent

M ode C o nt r ol

T i m e r / E v ent C ount e r 0

P r el oad R e gi s t er

Ti m e r / E v e nt

C ount e r 0

Da t a B u s

R e l oad

O v er f l ow

t o I nt e r r up t

1/ 2

8- s t age P r e s c a l e r

8- 1 M U X

f SY S

f IN T

PS C 2 ~ P SC 0

f RT C

R O M C ode O p t i on

( 1 /2 ~ 1 /2 5 6 )

Timer/Event Counter 0

TM 1

TM 0

TM R 1

TM 1

TM 0

TO N

P u l s e W i dt h

M eas ur e m ent

M ode C o nt r ol

16 B i t s

T i m e r / E v ent C ount e r

P r el oad R e gi s t er

Da t a B u s

R e l oad

O v er f l ow

to I nte r r u p t

f SY S/ 4

f RT C

R O M C ode O p t i on

16 B i t s

T i m e r / E v ent C ount e r

( T M R 1H / T M R 1L)

Low B y t e

Bu f f e r

Timer/Event Counter 1

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