W78E516B_06 Datasheet, PDF (5/37 Pages) Winbond – 8-BIT MICROCONTROLLER

W78E516B
4. PIN DESCRIPTION
SYMBOL
EA
TYPE
DESCRIPTIONS
EXTERNAL ACCESS ENABLE: This pin forces the processor to execute the
I ^{external ROM. The ROM address and data will not be presented on the bus if}
the EA pin is high.
PSEN
ALE
RST
XTAL1
XTAL2
VSS
VDD
P0.0 − P0.7
P1.0 − P1.7
P2.0 − P2.7
P3.0 − P3.7
P4.0 − P4.3
OH
OH
IL
I
O
I
I
I/O D
I/O H
I/O H
I/O H
I/O H
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 originate 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
oscillator frequency.
RESET: A high on this pin for two machine cycles while the oscillator is
running 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: Function is the same as that of standard 8052.
PORT 1: Function is the same as that of standard 8052.
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: Function is the same as that of the standard 8052.
PORT 4: A bi-directional I/O. See details below.
* Note: TYPE I: input, O: output, I/O: bi-directional, H: pull-high, L: pull-low, D: open drain
PORT4
Another bit-addressable port P4 is also available and only 4 bits (P4<3:0>) can be used. This port
address is located at 0D8H with the same function as that of port P1.
Example:
P4
REG 0D8H
MOV P4, #0AH
; Output data "A" through P4.0 − P4.3.
MOV A, P4
; Read P4 status to Accumulator.
ORL P4, #00000001B
ANL P4, #11111110B
Publication Release Date: December 4, 2006
-5-
Revision A11