HT82K68 datasheet(16/40 Pages) HOLTEK

16 / 40 page

HT82K68E

August 8, 2000

Preliminary

Label

Bits

Function

0~3

Unused bits, read as "0"

TON

To enable/disable timer counting

(0= disabled; 1= enabled)

Unused bits, read as "0"

TM0

TM1

10= Timer mode (internal clock)

TMRC register

To enable the counting operation, the timer

ON bit (TON; bit 4 of TMRC) should be set to 1.

In the case of timer counter OFF condition,

writing data to the timer counter preload reg-

ister will also reload that data to the timer

counter. But if the timer counter is turned on,

data written to it will only be kept in the

timer counter preload register. The timer coun-

ter will still operate until overflow occurs. When

the timer counter (reading TMR) is read, the

clock will be blocked to avoid errors. As clock

blocking may results in a counting error, this

must be taken into consideration by the program-

mer.

Input/output ports

There are 32 bidirectional input/output lines in

the HT82K68E, labeled from PA to PE, which

are mapped to the data memory of [12H], [14H],

[16H], [18H] and [1AH] respectively. All these

I/O ports can be used for input and output opera-

tions. For input operation, these ports are

non-latching, that is, the inputs must be ready

at the T2 rising edge of instruction MOV A,[m]

(m=12H, 14H, 16H, 18H or 1AH). For output op-

eration, all data is latched and remains un-

changed until the output latch is rewritten.

S yst e m C l o ck/ 4

TM 1

TM 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 ont r o l

T i m e r C o unt er

P r el oad R e gi s t er

Ti m e r

C ount e r

Da t a B u s

R e l oad

O v er f l ow

t o I nt er r u p t

Timer counter

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