HT48R02B datasheet(29/71 Pages) HOLTEK

29 / 71 page

HT46R01B/02B/01N/02N

HT48R01B/02B/01N/02N

Rev.1.10

February 12, 2010

Input/Output Ports

Holtek microcontrollers offer considerable flexibility on

their I/O ports. Most pins can have either an input or out-

put designation under user program control. Addi-

tionally, as there are pull-high resistors and wake-up

software configurations, the user is provided with an I/O

structure to meet the needs of a wide range of applica-

tion possibilities.

For input operation, these ports are non-latching, which

means the inputs must be ready at the T2 rising edge of

instruction

²MOV A,[m]², where m denotes the port ad-

dress. For output operation, all the data is latched and

remains unchanged until the output latch is rewritten.

Pull-high Resistors

Many product applications require pull-high resistors for

their switch inputs usually requiring the use of an external

resistor. To eliminate the need for these external resis-

tors, when configured as an input have the capability of

being connected to an internal pull-high resistor. These

pull-high resistors are selectable via a register known as

PAPU located in the Data Memory. The pull-high resis-

tors are implemented using weak PMOS transistors.

Note that pin PA7 does not have a pull-high resistor se-

lection.

Port A Wake-up

If the HALT instruction is executed, the device will enter

the Sleep Mode, where the system clock will stop result-

ing in power being conserved, a feature that is important

for battery and other low-power applications. Various

methods exist to wake-up the microcontroller, one of

which is to change the logic condition on one of the

PA0~PA7 pins from high to low. After a HALT instruction

forces the microcontroller into entering the Sleep Mode,

the processor will remain in a low-power state until the

logic condition of the selected wake-up pin on Port A

changes from high to low. This function is especially suit-

able for applications that can be woken up via external

switches. Note that pins PA0 to PA7 can be selected indi-

vidually to have this wake-up feature using an internal

· PAWK, PAC, PAPU Register

Name

POR

Bit

76543210

PAWK

00H

PAWK7

PAWK6

PAWK5

PAWK4

PAWK3

PAWK2

PAWK1

PAWK0

PAC

FFH

PAC7

PAC6

PAC5

PAC4

PAC3

PAC2

PAC1

PAC0

PAPU

00H

PAPU6

PAPU5

PAPU4

PAPU3

PAPU2

PAPU1

PAPU0

²¾² Unimplemented, read as ²0²

PAWKn: PA wake-up function enable

0: disable

1: enable

PACn: I/O type selection

0: output

1: input

PAPUn: Pull-high function enable

0: disable

1: enable

· PBPU Register

Name

POR

Bit

76543210

PBC

FFH

¾¾¾¾¾¾

PBC1

PBC0

PBPU

00H

¾¾¾¾¾¾

PBPU1

PBPU0

²¾² Unimplemented, read as ²0²

PBCn: I/O type selection

0: output

1: input

PBPUn: Pull-high function enable

0: disable

1: enable

HT48R02B Datasheet(PDF) 29 Page - Holtek Semiconductor Inc

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