HT56R26 View Datasheet(PDF) - Holtek Semiconductor
Part Name
Description
MFG CO.
'HT56R26' PDF : 134 Pages View PDF
HT56R22/HT56R23/HT56R24/HT56R25/HT56R26
D a ta B u s
W r ite C o n tr o l R e g is te r
C h ip R e s e t
R e a d C o n tr o l R e g is te r
W r ite D a ta R e g is te r
R e a d D a ta R e g is te r
C o n tr o l B it
DQ
P u ll- H ig h
S e le c t
CK Q
S
V DD
W eak
P u ll- u p
D a ta B it
DQ
CK Q
S
M
U
X
V D D /2
C O M nE N
SCO M EN
PB Input/Output Port
P B 0 /S C O M 0 ~
P B 3 /S C O M 3
I/O Pin Structures
The diagrams illustrate the I/O pin internal structures. As
the exact logical construction of the I/O pin may differ
from these drawings, they are supplied as a guide only
to assist with the functional understanding of the I/O
pins.
Programming Considerations
Within the user program, one of the first things to con-
sider is port initialisation. After a reset, the I/O data reg-
ister and I/O 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
port control registers, are then programmed to setup
some pins as outputs, these output pins will have an ini-
tial high output value unless the associated port data
register is first programmed. Selecting which pins are in-
puts 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 reg-
ister using the ²SET [m].i² and ²CLR [m].i² instructions.
Note that when using these bit 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 re-
write this data back to the output ports.
S y s te m C lo c k
T1
T2
T3
T4
T1
T2
T3
T4
P o rt D a ta
R e a d fro m P o rt
W r ite to P o r t
Read Modify Write Timing
Pins PA0 to PA7 each have a wake-up functions, se-
lected via the PAWK register. When the device is in the
Idle/Sleep Mode, various methods are available to wake
the device up. One of these is a high to low transition of
any of the these pins. Single or multiple pins on Port A
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. The devices contain several
8-bit and 16-bit count-up timers. As each timer has three
different operating modes, they can be configured to op-
erate as a general timer, an external event counter or as
a pulse width measurement device. The provision of a
prescaler to the clock circuitry of the 8-bit Timer/Event
Counter also gives added range to this timer.
There are two types of registers related to the
Timer/Event Counters. The first are the registers that
contain the actual value of the Timer/Event Counter and
into which an initial value can be preloaded. Reading
from these registers retrieves the contents of the
Timer/Event Counter. 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. The Timer/Event Counters can
have the their clock configured to come from an internal
clock source. In addition, their clock source can also be
configured to come from an external timer pin.
Rev. 1.30
46
December 26, 2014
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