HT46801N-1 Holtek Semiconductor, HT46801N-1 Datasheet - Page 29

• Manufacturer Part Number: HT46801N-1
• Description: (HT4xR01x-1) Small Package 8-Bit OTP MCU
• Manufacturer: Holtek Semiconductor

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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 MOV A,[m] , 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-
Rev.1.00
I/O Port Register Lists
Register
PAWK
Name
PAPU
PBPU
PAC
PBC
POR
FFH
00H
00H
0FH
00H
PAWKn: PA wake-up function enable
PACn/PBCn: I/O type selection
PAPUn/PBPUn: Pull-high function enable
0: disable
1: enable
0: output
1: input
0: disable
1: enable
Unimplemented, read as 0
PAWK7
PAC7
7
PAWK6
PAPU6
PAC6
6
PAWK5
PAPU5
PAC5
5
29
PAWK4
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
register known as PAWK, located in the Data Memory.
PAPU4
PAC4
4
Bit
PAWK3
PAPU3
PAC3
3
HT46R01B-1/HT46R01N-1
HT48R01B-1/HT48R01N-1
PAWK2
PAPU2
PAC2
2
PAWK1
PAPU1
PBPU1
PAC1
PBC1
1
June 9, 2011
PAWK0
PAPU0
PBPU0
PAC0
PBC0
0
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