W78E516DDG Datasheet, PDF (9/90 Pages) Nuvotem Talema – 8-BIT MICROCONTROLLER

W78E516D/W78E058D Data Sheet
5 PIN DESCRIPTIONS
SYMBOL
EA
PSEN
ALE
RST
XTAL1
XTAL2
VSS
VDD
P0.0−P0.7
P1.0−P1.7
P2.0−P2.7
P3.0−P3.7
TYPE
I
OH
OH
IL
I
O
I
I
I/O D
I/O H
I/O H
I/O H
DESCRIPTIONS
EXTERNAL ACCESS ENABLE: This pin forces the processor to execute the
external ROM. The ROM address and data will not be present on the bus if the
EA pin is high and the program counter is within the internal ROM area. Oth-
erwise they will be present on the bus.
PROGRAM STORE ENABLE: PSEN enables the external ROM data in the
Port 0 address/data bus.
When internal ROM access is performed, no PSEN strobe signal outputs ori-
ginate from this pin.
ADDRESS LATCH ENABLE: ALE is used to enable the address latch that
separates the address from the data on Port 0. ALE runs at 1/6th of the oscilla-
tor frequency. An ALE pulse is omitted during external data memory accesses.
RESET: A high on this pin for two machine cycles while the oscillator is run-
ning resets the device.
CRYSTAL 1: This is the crystal oscillator input. This pin may be driven by an
external clock.
CRYSTAL 2: This is the crystal oscillator output. It is the inversion of XTAL1.
GROUND: ground potential.
POWER SUPPLY: Supply voltage for operation.
PORT 0: Port 0 is an open-drain bi-directional I/O port. This port also pro-
vides a multiplexed low order address/data bus during accesses to external
memory.
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
PORT 2: Port 2 is a bi-directional I/O port with internal pull-ups. This port also
provides the upper address bits for accesses to external memory.
PORT 3: Port 3 is a bi-directional I/O port with internal pull-ups. All bits have
alternate functions, which are described below:
RXD(P3.0): Serial Port 0 input
TXD(P3.1): Serial Port 0 output
INT0 (P3.2) : External Interrupt 0
INT1 (P3.3) : External Interrupt 1
T0(P3.4) : Timer 0 External Input
T1(P3.5) : Timer 1 External Input
WR _{(P3.6) : External Data Memory Write Strobe}
P4.0−P4.3
I/O H
RD _{(P3.7) : External Data Memory Read Strobe}
PORT 4: Another bit-addressable bidirectional I/O port P4. P4.3 and P4.2 are
alternative function pins. It can be used as general I/O port or external interrupt
input sources ( INT2 / INT3 ).
* Note : TYPE I: input, O: output, I/O: bi-directional, H: pull-high, L: pull-low, D: open drain
Publication Release Date: Feb 15, 2011
-9-
Revision A09