W78E51B-40 WINBOND [Winbond], W78E51B-40 Datasheet - Page 3

• Manufacturer Part Number: W78E51B-40
• Description: 8-BIT MTP MICROCONTROLLER
• Manufacturer: WINBOND [Winbond]

PIN DESCRIPTION
P0.0 P0.7 PORT 0: Port 0 is a bi-directional I/O port which also provides a multiplexed low order
P1.0 P1.7 PORT 1: Port 1 is a bi-directional I/O port with internal pull-ups. The bits have alternate
P2.0 P2.7 PORT 2: Port 2 is a bi-directional I/O port with internal pull-ups. This port also provides
P3.0 P3.7 PORT 3: Port 3 is a bi-directional I/O port with internal pull-ups. All bits have alternate
P4.0 P4.3 PORT 4: Another bit-addressable bidirectional I/O port P4. P4.3 and P4.2 are
SYMBOL
XTAL1
XTAL2
PSEN
RST
ALE
V
V
EA
DD
SS
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 and
data will not be presented on the bus if EA pin is high and the program counter is
within on-chip ROM area.
PROGRAM STORE ENABLE: PSEN enables the external ROM data onto the Port 0
address/ data bus during fetch and MOVC operations. When internal ROM access is
performed, no PSEN strobe signal outputs from this pin.
ADDRESS LATCH ENABLE: ALE is used to enable the address latch that separates
the address from the data on Port 0.
RESET: A high on this pin for two machine cycles while the oscillator is running resets
the device.
CRYSTAL1: This is the crystal oscillator input. This pin may be driven by an external
clock.
CRYSTAL2: This is the crystal oscillator output. It is the inversion of XTAL1.
GROUND: Ground potential
POWER SUPPLY: Supply voltage for operation.
address/data bus during accesses to external memory. The pins of Port 0 can be
individually configured to open-drain or standard port with internal pull-ups.
functions which are described below:
the upper address bits for accesses to external memory.
functions, which are described below:
RXD(P3.0) : Serial Port receiver input
TXD(P3.1) : Serial Port transmitter output
T0(P3.4)
T1(P3.5)
alternative function pins. It can be used as general I/O port or external interrupt input
sources ( INT2 / INT3 ).
INT0 (P3.2) : External Interrupt 0
INT1 (P3.3) : External Interrupt 1
RD (P3.7) : External Data Memory Read Strobe
WR (P3.6) : External Data Memory Write Strobe
T2(P1.0): Timer/Counter 2 external count input
T2EX(P1.1): Timer/Counter 2 Reload/Capture control
: Timer 0 External Input
: Timer 1 External Input
DESCRIPTIONS
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Preliminary W78E51B
Publication Release Date: December 1998
Revision A1