HT83XXX

Rev. 0.10

17

August 25, 2003

Preliminary

Input/Output Ports

There are 8 bidirectional input/output lines in the

microcontroller, labeled from PA, which are mapped to

the data memory of [12H] respectively. All of these I/O

ports can be used for input and output operations. For

input operation, these ports are non-latching, that is, the

inputs must be ready at the T2 rising edge of instruction

²MOV A, [m]² (m=12H). For output operation, all the

data is latched and remains unchanged until the output

latch is rewritten.

Each I/O line has its own control register (PAC) to con-

trol the input/output configuration. With this control reg-

ister, CMOS output or Schmitt trigger input with or

without pull-high resistor structures can be reconfigured

dynamically under software control. To function as an in-

put, the corresponding latch of the control register must

write

²1². The input source also depends on the control

register. If the control register bit is

²1², the input will

read the pad state. If the control register bit is

²0², the

contents of the latches will move to the internal bus. The

latter is possible in the

²read-modify-write² instruction.

For output function, CMOS is the only configuration.

These control registers are mapped to locations 13H.

After a chip reset, these input/output lines remain at high

levels or floating state (dependent on pull-high options).

Each bit of these input/output latches can be set or

cleared by

²SET [m].i² and ²CLR [m].i² (m=12H) instruc-

tions.

Some instructions first input data and then follow the

output operations. For example,

²SET [m].i², ²CLR

[m].i

², ²CPL [m]², ²CPLA [m]² read the entire port states

into the CPU, execute the defined operations

(bit-operation), and then write the results back to the

latches or the accumulator.

Each line of port A has the capability of waking-up the

device. The wake-up capability of port A is determined

by mask option. There is a pull-high option available for

all I/O lines. Once the pull-high option is selected, all I/O

lines have pull-high resistors. Otherwise, the pull-high

resistors are absent. It should be noted that a

non-pull-high I/O line operating in input mode will cause

a floating state.

Q

D

C K

S

Q

Q

D

C K

S

Q

M

U

X

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 I / O

R e a d I / O

S y s t e m W a k e - U p ( P A o n l y )

W e a k

P u l l - u p

P A 0 ~ P A 7

M a s k O p t i o n

M a s k O p t i o n

Input/Output Ports