EF6805U3 Datasheet, PDF (5/31 Pages) STMicroelectronics – 8-BIT MICROCOMPUTER UNIT

Figure 2 : TTL Equivalent Test Load (port B).
EF6805U3
Figure 3 : CMOS Equivalent Test Load (port A).
Figure 4 : TTL Equivalent Test Load (port A
andC).
Figure 5 : Open-drain Equivalent Test Load (port
C).
SIGNAL DESCRIPTION
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. V_CC is power and V_SS is the ground
connection.
INT - This pin provides the capability for asynchro-
nously applying an external interrupt to the MCU.
Refer to Interrupts Section for additional informa-
tion.
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
these inputs.
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-
tional information.
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