ht82k70e-l Holtek Semiconductor Inc., ht82k70e-l Datasheet - Page 16

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

Output Pin Slew Rate Control
The output pin slew rate can be setup using a configura-
tion option and can be set to be either 0ns, 50ns, 100ns
or 200ns.
I/O Pin Structures
The accompanying diagrams illustrate the internal
structures of some I/O pin types. As the exact logical
construction of the I/O pin will differ from these draw-
ings, they are supplied as a guide only to assist with the
functional understanding of the I/O pins. The wide range
of pin-shared structures does not permit all types to be
shown.
Programming Considerations
Within the user program, one of the first things to con-
sider is port initialisation. After a reset, all of the data and
port control register will be set high. This means that all
I/O pins will default to an input state, the level of which
depends on the other connected circuitry and whether
pull-high options have been selected. If the PAC, PBC,
PCC, PDC, PEC and PFC.0~PFC.2 port control regis-
ter, are then programmed to setup some pins as out-
puts, these output pins will have an initial high output
value unless the associated PA, PB, PC, PD, PE and
PF0~PF2 port data registers are first programmed. Se-
lecting which pins are inputs and which are outputs can
be achieved byte-wide by loading the correct value into
the port control register or by programming individual
bits in the port control register using the SET [m].i and
control instructions, a read-modify-write operation takes
place. The microcontroller must first read in the data on
the entire port, modify it to the required new bit values
and then rewrite this data back to the output ports.
All I/O pins has the additional capability of providing
wake-up functions. When the device is in the Power
Down Mode, various methods are available to wake the
device up. One of these is a high to low or low to high
transition of any of all I/O pins. Single or multiple pins on
all I/O pins can be setup to have this function.
Timer/Event Counters
The provision of timers form an important part of any
microcontroller, giving the designer a means of carrying
out time related functions. This device contains two
count-up timers of 16-bit capacities. As each timer has
three different operating modes, they can be configured
Rev. 1.00
CLR [m].i instructions. Note that when using these bit
Read/Write Timing
16
to operate as a general timer, an external event counter
or as a pulse width measurement device.
There are two types of registers related to the
Timer/Event Counters. The first is the register that con-
tain the actual value of the Timer/Event Counter and into
which an initial value can be preloaded, and is known as
TMR0H/TMR0L, TMR1H/TMR1L. Reading from this
register retrieves the contents of the Timer/Event Coun-
ter. The second type of associated register is the Timer
Control Register, which defines the timer options and
determines how the Timer/Event Counter is to be used,
and has the name TMR0C or TMR1C. This device can
have the timer clocks configured to come from the inter-
nal clock sources. In addition, the timer clock sources
can also be configured to come from the external timer
pins.
The external clock source is used when the Timer/Event
Counter is in the event counting mode, the clock source
being provided on the external timer pin. The external
timer pin has the name TMR0 or TMR1. Depending
upon the condition of the T0E or T1E bit in the Timer
Control Register, each high to low, or low to high transi-
tion on the external timer input pin will increment the
Timer/Event Counter by one.
Configuring the Timer/Event Counter Input Clock
Source
The Timer/Event Counter s clock can originate from vari-
ous sources. The instruction clock source or WDTOSC
(system clock source divided by 4) is used when the
Timer/Event Counter 0 or Timer/Event Counter 1 is in the
timer mode or in the pulse width measurement mode.
The external clock source is used when the Timer/Event
Counter is in the event counting mode, the clock source
being provided on the external timer pin, TMR0 or TMR1.
Depending upon the condition of the T0E or T1E bit, each
high to low, or low to high transition on the external timer
pin will increment the counter by one.
Timer Registers - TMR0H/TMR0L, TMR1H/TMR1L
The timer registers are special function registers located
in the Special Purpose RAM Data Memory and are the
places where the actual timer values are stored. The
timer registers are known as TMR0L/ TMR0H, TMR1L
/TMR1H. The value in the timer registers increases by
one each time an internal clock pulse is received or an
external transition occurs on the external timer pin. The
timer will count from the initial value loaded by the
preload register to the full count of FFFFH for the 16-bit
timer at which point the timer overflows and an internal
interrupt signal is generated. The timer value will then
be reset with the initial preload register value and con-
tinue counting.
To achieve a maximum full range count of FFFFH, the
preload registers must first be cleared to all zeros. It
should be noted that after power-on, the preload register
HT82K70E-L/HT82K76E-L
September 15, 2009