ht82k70e-l Holtek Semiconductor Inc., ht82k70e-l Datasheet - Page 14

• Manufacturer Part Number: ht82k70e-l
• Description: I/o Type 8-bit Otp Mcu
• Manufacturer: Holtek Semiconductor Inc.

In addition, on entering an interrupt sequence or execut-
ing a subroutine call, the status register will not be
pushed onto the stack automatically. If the contents of
the status registers are important and if the interrupt rou-
tine can change the status register, precautions must be
taken to correctly save it.
Interrupt Control Registers - INTC0, INTC1
The microcontrollers provide one external interrupts, two
internal timer/event counter overflow interrupt and one
SPI interrupt. By setting various bits within this register
using standard bit manipulation instructions, the en-
able/disable function of each interrupt can be independ-
ently controlled. A master interrupt bit within this register,
the EMI bit, acts like a global enable/disable and is used
to set all of the interrupt enable bits on or off. This bit is
cleared when an interrupt routine is entered to disable
further interrupt and is set by executing the RETI in-
struction.
Timer/Event Counter Registers -
TMR0H/TMR1H, TMR0L/TMR1L,TMR0C/TMR1C
All devices possess two internal 16-bit count-up timer. An
associated register pair known as TMR0L(TMR1L)/
TMR0H(TMR1H) is the location where the timer 16-bit
value is located. This register can also be preloaded with
fixed data to allow different time intervals to be setup. An
associated control register, known as TMR0C(TMR1C),
contains the setup information for this timer, which deter-
mines in what mode the timer is to be used as well as
containing the timer on/off control function.
Input/Output Ports and Control Registers
Within the area of Special Function Registers, the I/O
registers and and their associated control registers play
a prominent role. All I/O ports have a designated regis-
ter correspondingly labeled as PA, PB, PC, PD, PE and
PF0~PF2. These labeled I/O registers are mapped to
specific addresses within the Data Memory as shown in
the Data Memory table, which are used to transfer the
appropriate output or input data on that port. With each
I/O port there is an associated control register labeled
PAC, PBC, PCC, PDC, PEC and PFC.0~PFC.2, also
mapped to specific addresses with the Data Memory.
The control register specifies which pins of that port are
set as inputs and which are set as outputs. To setup a
pin as an input, the corresponding bit of the control reg-
ister must be set high, for an output it must be set low.
During program initialization, it is important to first setup
the control registers to specify which pins are outputs
and which are inputs before reading data from or writing
data to the I/O ports. One flexible feature of these regis-
ters is the ability to directly program single bits using the
change I/O pins from output to input and vice versa by
Rev. 1.00
SET [m].i and CLR [m].i instructions. The ability to
14
manipulating specific bits of the I/O control registers dur-
ing normal program operation is a useful feature of
these devices.
Input/Output Ports
Holtek microcontrollers offer considerable flexibility on
their I/O ports. With the input or output designation of ev-
ery pin fully under user program control, pull-high op-
tions for all ports and wake-up options on certain pins,
the user is provided with an I/O structure to meet the
needs of a wide range of application possibilities.
Depending upon which package is chosen, the
microcontroller provides up to 43 bidirectional input/out-
put lines labeled with port names PA, PB, PC, PD, PE
and PF0~PF2.
This register is mapped to the Data Memory with an ad-
dresses as shown in the Special Purpose Data Memory
table. Seven of these I/O lines can be used for input and
output operations and one line as an input only. For in-
put 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 exter-
nal resistor. To eliminate the need for these external re-
sistors, I/O pins, when configured as an input have the
capability of being connected to an internal pull-high re-
sistor. The pull-high resistors are selectable via configu-
ration options and are implemented using weak PMOS
transistors. Each pin on all of I/O can be selected indi-
vidually to have this pull-high resistors feature and each
nibble on each of the other ports.
Port Pin Wake-up
If the HALT instruction is executed, the device will enter
the Power Down Mode, where the system clock will stop
resulting in power being conserved, a feature that is im-
portant 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 Port pins from high to low or low to high. After a
HALT instruction forces the microcontroller into entering
the Power Down Mode, the processor will remain idle or
in a low-power state until the logic condition of the se-
lected wake-up pin on Port pins changes from high to
low or low to high. This function is especially suitable for
applications that can be woken up via external switches.
Note that each pin on PA, PB, PC, PD, PE and PF0~PF2
can be selected individually to have this wake-up fea-
ture.
HT82K70E-L/HT82K76E-L
September 15, 2009