Daewoo DHC - 2300K, Service Manual

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27
Component Descriptions
* PIN DESCRIPTION
SYMBOL DESCRIPTIONS
EA#
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.
PSEN#
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.
ALE
ADDRESS LATCH ENABLE: ALE is used to enable the address latch that separates
the address from the data on Port 0.
RST
RESET: A high on this pin for two machine cycles while the oscillator is running
resets
the device.
XTAL1
CRYSTAL1: This is the crystal oscillator input. This pin may be driven by an external
clock.
XTAL2 CRYSTAL2: This is the crystal oscillator output. It is the inversion of XTAL1.
VSS GROUND: Ground potential
VDD POWER SUPPLY: Supply voltage for operation.
P0.0 - P0.7
PORT 0: Port 0 is a bi-directional I/O port which also provides a multiplexed low
order
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.
P1.0 - P1.7
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 control
P2.0 - P2.7
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.
P3.0 - P3.7
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 receiver input
TXD(P3.1) : Serial Port transmitter 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
RD(P3.7) : External Data Memory Read Strobe
P4.0 - P4.3
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 ).