ht82j31a Holtek Semiconductor Inc., ht82j31a Datasheet - Page 13

• Manufacturer Part Number: ht82j31a
• Description: 16 Channel A/d Mcu With Spi Interface
• Manufacturer: Holtek Semiconductor Inc.

For the I/O pin to function as an input, the corresponding
bit of the control register must be written as a 1 . This
will then allow the logic state of the input pin to be di-
rectly read by instructions. When the corresponding bit
of the control register is written as a 0 , the I/O pin will
be setup as a CMOS output. If the pin is currently setup
as an output, instructions can still be used to read the
output register. However, it should be noted that the pro-
gram will in fact only read the status of the output data
latch and not the actual logic status of the output pin.
Pin-shared Functions
The flexibility of the microcontroller range is greatly en-
hanced by the use of pins that have more than one func-
tion. Limited numbers of pins can force serious design
constraints on designers but by supplying pins with
multi-functions, many of these difficulties can be over-
come. For some pins, the chosen function of the
multi-function I/O pins is set by configuration options
while for others the function is set by application pro-
gram control.
Rev. 1.00
External Interrupt Input_A
The external interrupt pin INTA is pin-shared with the
I/O pin PA5. For applications not requiring an external
interrupt input, the pin-shared external interrupt pin
can be used as a normal I/O pin, however to do this,
the external interrupt enable bits in the INTC register
must be disabled.
External Interrupt Input_B
The external interrupt pin INTB is pin-shared with the
I/O pin PA6. For applications not requiring an external
Input/Output Ports
13
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.
interrupt input, the pin-shared external interrupt pin
can be used as a normal I/O pin, however to do this,
the external interrupt enable bits in the INTC1 register
must be disabled.
External Timer Clock Input
The external timer pin TMR is pin-shared with the I/O
pin PA4. To configure this pin to operate as timer input,
the corresponding control bits in the timer control reg-
ister must be correctly set. For applications that do not
require an external timer input, this pin can be used as
a normal I/O pin. Note that if used as a normal I/O pin
the timer mode control bits in the timer control register
must select the timer mode, which has an internal
clock source, to prevent the input pin from interfering
with the timer operation.
PFD Output
Each device contains a PFD function whose single
output is pin-shared with PA3. The output function of
this pin is chosen via a configuration option and re-
mains fixed after the device is programmed. Note that
the corresponding bit of the port control register,
PAC.3, must setup the pin as an output to enable the
PFD output. If the PAC port control register has setup
the pin as an input, then the pin will function as a nor-
mal logic input with the usual pull-high option, even if
the PFD configuration option has been selected.
September 19, 2007
HT82J31A