HT48R005 Datasheet, PDF (28/62 Pages) Holtek Semiconductor Inc – Small Package 8-Bit OTP MCU

HT48R005/HT46R005
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~PA2, PA5~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 es-
pecially suitable for applications that can be woken up
via external switches. Note that pins PA0~PA2,
PA5~PA7 can be selected individually to have this
wake-up feature using an internal register known as
PAWK, located in the Data Memory.
· PAWK, PAC, PAPU Register
Register
Name
PAWK
PAC
PAPU
POR
00H
FFH
00H
7
PAWK7
PAC7
¾
6
PAWK6
PAC6
PAPU6
5
PAWK5
PAC5
PAPU5
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
Bit
4
3
¾
¾
¾
¾
¾
¾
2
PAWK2
PAC2
PAPU2
1
PAWK1
PAC1
PAPU1
0
PAWK0
PAC0
PAPU0
Rev. 1.00
28
November 29, 2011