HT86B40 datasheet(37/83 Pages) HOLTEK

37 / 83 page

HT86BXX/HT86BRXX

Rev. 1.70

February 22, 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, PDC, 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, PD, 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. The devices in the Voice Type

MCU series contain either three or four count up timers

of either 8 or 16-bit capacity depending upon which de-

vice is selected. The provision of an internal prescaler to

the clock circuitry of some of the timer gives added

range to the timer.

There is single type of register related to the 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 contents of the

Timer. All devices can have the timer clock configured to

come from the internal clock source. The accompanying

table lists the associated timer register names.

HT86B03

HT86B10

HT86BR10

HT86B20

HT86B30

HT86BR30

HT86B40

HT86B50

HT86B60

HT86BR60

HT86B70

HT86B80

HT86B90

No. of 8-bit Timers

Timer Register Name

TMR0

TMR1

TMR3

TMR0

TMR1

TMR3

Timer Control Register

TMR0C

TMR1C

TMR3C

TMR0C

TMR1C

TMR3C

No. of 16-bit Timers

Timer Register Name

TMR2L

TMR2H

Timer Control Register

TMR2C

Configuring the Timer Input Clock Source

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

divided by four while the 16-bit timer has a choice of ei-

ther the system clock or the system clock divided by

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

the division ratio of which is conditioned by the three

lower bits of the associated timer control register.

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

T 3 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 3 P S C 2 ~ T 3 P S C 0

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 T i m e r

f S Y S / 4

P r e s c a l e r

( 1 / 2 ~ 1 / 2 5 6 )

T 3 T M 1

T 1 T M 1

T 0 T M 1

T 3 T M 0

T 1 T M 0

T 0 T M 0

8-bit Timer Structure

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