Figure 2 : TTL Equivalent Test Load (port B).
Figure 3 : CMOS Equivalent Test Load (port A).
Figure 4 : TTL Equivalent Test Load (port A
Figure 5 : Open-drain Equivalent Test Load (port
The input and output signals for the MCU, shown in
figure 1, are described in the following paragraphs.
VCC AND VSS - Power is supplied to the MCU using
these two pins. VCC is power and VSS is the ground
INT - This pin provides the capability for asynchro-
nously applying an external interrupt to the MCU.
Refer to Interrupts Section for additional informa-
XTAL AND EXTAL - These pins provide control in-
put for theon-chip clock oscillator circuit. A crystal,
a resistor, or an external signal, depending on user
selectable manufacturing mask option, can be
connected to these pins to provide a system clock
with various degrees of stability/cost tradeoffs. Lead
length and stray capacitance on these two pins
should be minimized. Refer to Internal Clock Gen-
erator Options Section for recommendations about
NOTE : Pin 7 in DIL package/pin 8 in PLCC
package is connected to internal protection.
TIMER - The pin allows an external input to be used
to control the internal timer circuitry and also to ini-
tiate the self test program. Refer to Timer Section for
additional information about the timer circuitry.
RESET - This pin allows resetting of the MCU at
times other than the automatic resetting capability
already in the MCU. The MCU can be reset by pul-
ling RESET low. Refer to Resets Section for addi-