HT83F02 datasheet(21/64 Pages) HOLTEK

21 / 64 page

HT83F02

Rev. 1.20

November 19, 2010

Programming Considerations

Within the user program, one of the first things to con-

sider is port initialization. After a reset, all of the I/O data

and port control registers will be set high. This means

that all I/O pins will default to an input state, the level of

which depends on the other connected circuitry and

whether pull-high options have been selected. If the port

control registers, PAC, PBC, PCC etc., are then pro-

grammed to setup some pins as outputs, these output

pins will have an initial high output value unless the as-

sociated port data registers, PA, PB, PC etc., are first

programmed. Selecting which pins are inputs and which

are outputs can be achieved byte-wide by loading the

correct values into the appropriate port control register

or by programming individual bits in the port control reg-

ister using the

²SET [m].i² and ²CLR [m].i² instructions.

Note that when using these bit control instructions, a

read-modify-write operation takes place. The

microcontroller must first read in the data on the entire

port, modify it to the required new bit values and then re-

write this data back to the output ports.

Port A has the additional capability of providing wake-up

functions. When the device is in the Power Down Mode,

various methods are available to wake the device up.

One of these is a high to low transition of any of the Port

A pins. Single or multiple pins on Port A can be setup to

have this function.

Timers

The provision of timers form an important part of any

microcontroller, giving the designer a means of carrying

out time related functions. These devices contain two

count up timers of 8-bit capacity. The provision of an in-

ternal prescaler to the clock circuitry of the timer gives

added range to the timer.

There are two types of register related to each Timer.

The first is the register that contains the actual value of

the timer and into which an initial value can be

preloaded. Reading from this register retrieves the con-

tents of the Timer. All devices can have the timer clock

configured to come from the internal clock source.

Configuring the Timer Input Clock Source

The clock source for the 8-bit timers is the system clock

divided by four. The 8-bit timer clock source is also first di-

vided by a, the division ratio of which is conditioned by the

three lower bits of the associated timer control register.

Timer Registers

- TMR0, TMR1

The timer registers are special function registers located

in the special purpose Data Memory and is the place

where the actual timer value is stored. All devices con-

tain two 8-bit timers, whose registers are known as

TMR0 and TMR1. The value in the timer registers in-

creases by one each time an internal clock pulse is re-

ceived. The timer will count from the initial value loaded

by the preload register to the full count of FFH for the

8-bit timer at which point the timer overflows and an in-

ternal interrupt signal is generated. The timer value will

then be reset with the initial preload register value and

continue counting.

Note that to achieve a maximum full range count of FFH

for the 8-bit timer, the preload registers must first be

cleared to all zeros. It should be noted that after

power-on, the preload registers will be in an unknown

condition. Note that if the Timer Counters are in an OFF

condition and data is written to their preload registers,

this data will be immediately written into the actual coun-

ter. However, if the counter is enabled and counting, any

new data written into the preload data register during

this period will remain in the preload register and will

only be written into the actual counter the next time an

overflow occurs. Note also that when the timer registers

are read, the timer clock will be blocked to avoid errors,

however, as this may result in certain timing errors, pro-

grammers must take this into account.

T 1

T 2

T 3

T 4

T 1

T 2

T 3

T 4

W r i t e t o P o r t

R e a d f r o m P o r t

S y s t e m C l o c k

P o r t D a t a

Read/Write Timing

T i m e r M o d e C o n t r o l

T 0 O N

T 1 O N

P r e l o a d R e g i s t e r

T i m e r

D a t a B u s

R e l o a d

O v e r f l o w

t o I n t e r r u p t

T 1 P S C 2 ~ T 1 P S C 0

T 0 P S C 2 ~ T 0 P S C 0

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

f S Y S

P r e s c a l e r

( 1 / 2 ~ 1 / 2 5 6 )

T 1 T M 1

T 0 T M 1

T 1 T M 0

T 0 T M 0

8-bit Timer Structure

HT83F02 数据表(PDF) 21 Page - Holtek Semiconductor Inc

HT83F02 数据表(HTML) 21 Page - Holtek Semiconductor Inc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64

数据表下载