HT48R05A-1/HT48C05/HT48R06A-1/HT48C06/HT48R08A-1
In the case of timer/event counter OFF condition, writing
also depends on the control register. If the control regis-
ter bit is ²1², the input will read the pad state. If the con-
trol register bit is ²0², the contents of the latches will
move to the internal bus. The latter is possible in the
²read-modify-write² instruction.
data to the timer/event counter preload register will also
reload that data to the timer/event counter. But if the
timer/event counter is turned on, data written to it will
only be kept in the timer/event counter preload register.
The timer/event counter will still operate until overflow
occurs. When the timer/event counter (reading TMR) is
read, the clock will be blocked to avoid errors. As clock
blocking may results in a counting error, this must be
taken into consideration by the programmer.
For output function, CMOS is the only configuration.
These control registers are mapped to locations 13H,
15H and 17H.
After a chip reset, these input/output lines remain at high
levels or floating state (dependent on pull-high options).
Each bit of these input/output latches can be set or
cleared by ²SET [m].i² and ²CLR [m].i² (m=12H, 14H or
16H) instructions.
The bit0~2 of the TMRC can be used to define the
pre-scaling stages of the internal clock sources of the
timer/event counter. The definitions are as shown. The
overflow signal of the timer/event counter can be used
to generate PFD signals for buzzer driving.
Some instructions first input data and then follow the
output operations. For example, ²SET [m].i², ²CLR
[m].i², ²CPL [m]², ²CPLA [m]² read the entire port states
into the CPU, execute the defined operations
(bit-operation), and then write the results back to the
latches or the accumulator.
Input/Output Ports
There are 13 bidirectional input/output lines in the
microcontroller, labeled from PA to PC, which are
mapped to the data memory of [12H], [14H] and [16H]
respectively. All of these I/O ports can be used for input
and output operations. For input operation, these ports
are non-latching, that is, the inputs must be ready at the
T2 rising edge of instruction ²MOV A,[m]² (m=12H, 14H
or 16H). For output operation, all the data is latched and
remains unchanged until the output latch is rewritten.
Each line of port A has the capability of waking-up the
device. The highest 6-bit of port C and 5 bits of port B
are not physically implemented; on reading them a ²0² is
returned whereas writing then results in a no-operation.
See Application note.
There is a pull-high option available for all I/O lines.
Once the pull-high option is selected, all I/O lines have
pull-high resistors. Otherwise, the pull-high resistors are
absent. It should be noted that a non-pull-high I/O line
operating in input mode will cause a floating state.
Each I/O line has its own control register (PAC, PBC,
PCC) to control the input/output configuration. With this
control register, CMOS output or Schmitt trigger input
with or without pull-high resistor structures can be re-
configured dynamically (i.e. on-the-fly) under software
control. To function as an input, the corresponding latch
of the control register must write ²1². The input source
The PB0 and PB1 are pin-shared with BZ and BZ signal,
respectively. If the BZ/BZ option is selected, the output
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Input/Output Ports
Rev. 1.50
14
August 22, 2007
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
