HT83F40P datasheet(19/61 Pages) HOLTEK

19 / 61 page

HT83FXX

Rev. 1.00

May 12, 2009

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 etc., are then programmed

to setup some pins as outputs, these output pins will

have an initial high output value unless the associated

port data registers, PA, PB, 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 program-

ming individual bits in the port control register 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 re-

quired new bit values and then rewrite 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.

V D D

R e a d D a t a R e g i s t e r

C K

C o n t r o l B i t

P u l l - H i g h

O p t i o n

D a t a B u s

W r i t e C o n t r o l R e g i s t e r

C h i p R e s e t

R e a d C o n t r o l R e g i s t e r

W r i t e D a t a R e g i s t e r

D a t a B i t

P B D a t a B i t

P B 0 / S D O / S D A

P B 1 / S C K / S C L

P B 2 / S D I , P B 3 / S C S

A n a l o g S w i t c h O p t i o n

W e a k

P u l l - u p

P B 0 / S D O / S D A

P B 1 / S C K / S C L

P B 2 / S D I

P B 3 / S C S

PB Input/Output Port

W a k e - u p O p t i o n

S y s t e m W a k e - u p

R e a d D a t a R e g i s t e r

C o n t r o l B i t

P u l l - H i g h

O p t i o n

D a t a B u s

W r i t e C o n t r o l R e g i s t e r

C h i p R e s e t

R e a d C o n t r o l R e g i s t e r

W r i t e D a t a R e g i s t e r

D a t a B i t

P A 0 ~ P A 7

W e a k

P u l l - u p

C K

V D D

PA Input/Output Port

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

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