BS2824 Holtek Semiconductor Inc., BS2824 Datasheet - Page 46

• Manufacturer Part Number: BS2824
• Description: Touch Key Mcu
• Manufacturer: Holtek Semiconductor Inc.

BS2824/BS2854/BS2868
Touch Key MCU
Input/Output Ports
Rev. 1.00
Pull-high Resistors
Port A Wake-up
PAWK, PAC, PAPU, PBC, PBPU, PCC, PCPU, PDC, PDPU, PFC, PFPU Register
Holtek microcontrollers offer considerable flexibility on their I/O ports. Most pins can have either
an input or output designation under user program control. Additionally, 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 application 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 address. For output operation, all
the data is latched and remains unchanged until the output latch is rewritten.
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 resistors, 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, PBPU, PCPU, PDPU and PFPU located in the Data Memory.
The pull-high resistors are implemented using weak PMOS transistors. Note that pin PA7 does not
have a pull-high resistor selection.
If the HALT instruction is executed, the device will enter the Idle/Sleep Mode, where the system
clock will stop resulting 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 Idle/Sleep Mode, the processor will remain idle or 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 suitable for applications that can be woken up via external switches.
Note that pins PA0 to PA7 can be selected individually to have this wake-up feature using an internal
register known as PAWK, located in the Data Memory.
Register
BS2824
PAWKn: PA wake-up function enable
PACn/PBCn: I/O type selection
PAPUn/PBPUn: Pull-high function enable
PAWK
Name
PAPU
PBPU
PAC
PBC
0: disable
1: enable
0: output
1: input
0: disable
1: enable
Unimplemented, read as 0
POR
FFH
FFH
00H
00H
00H
PAWK7 PAWK6 PAWK5 PAWK4 PAWK3 PAWK2 PAWK1 PAWK0
PAC7
7
PAPU6
PAC6
6
46
PAPU5
PAC5
5
PAPU4
PAC4
4
Bit
PAPU3
PAC3
3
PAPU2
PAC2
2
PAPU1
PBPU1
PAC1
PBC1
January 27, 2010
1
PAPU0
PBPU0
PAC0
PBC0
0