W77L516A Datasheet, PDF (4/89 Pages) List of Unclassifed Manufacturers – 8-BIT MICROCONTROLLER

W77L516A
4. PIN DESCRIPTION
SYMBOL
EA
TYPE
DESCRIPTIONS
EXTERNAL ACCESS ENABLE: This pin forces the processor to execute out of
external ROM. It should be kept high to access internal ROM. The ROM address
I
and data will not be present on the bus if EA pin is high. Otherwise they will be
present on the bus.
PSEN
ALE
RST
XTAL1
XTAL2
VSS
VDD
P0.0−P0.7
P1.0−P1.7
PROGRAM STORE ENABLE: PSEN enables the external ROM data onto the
O Port 0 address/data bus during fetch and MOVC operations. When internal ROM
access is performed, no PSEN strobe signal outputs from this pin.
O
ADDRESS LATCH ENABLE: ALE is used to enable the address latch that
separates the address from the data on Port 0.
I
RESET: A high on this pin for two machine cycles while the oscillator is running
resets the device.
I
CRYSTAL1: This is the crystal oscillator input. This pin may be driven by an
external clock.
O CRYSTAL2: This is the crystal oscillator output. It is the inversion of XTAL1.
I GROUND: Ground potential
I POWER SUPPLY: Supply voltage for operation.
PORT 0: Port 0 is an open-drain bi-directional I/O port. This port also provides a
I/O ^{multiplexed low order address/data bus during accesses to external memory.}
Port 0 has internal pull-up resisters enabled by software.
PORT 1: Port 1 is a bi-directional I/O port with internal pull-ups. The bits have
alternate functions which are described below:
T2(P1.0): Timer/Counter 2 external count input
T2EX(P1.1): Timer/Counter 2 Reload/Capture/Direction control
RXD1(P1.2): Serial port 2 RXD
I/O _{TXD1(P1.3): Serial port 2 TXD}
INT2(P1.4): External Interrupt 2
INT3 (P1.5): External Interrupt 3
INT4(P1.6): External Interrupt 4
P2.0−P2.7
INT5 (P1.7): External Interrupt 5
PORT 2: Port 2 is a bi-directional I/O port with internal pull-ups. This port also
I/O
provides the upper address bits for accesses to external memory. The P2.6 and
P2.7 also provide the alternate function /REBOOT which is H/W reboot from LD
flash.
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